Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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METHOD AND APPARATUS FOR
MULTI-LINE SEISMIC EXPLORATION
BACKGROUND OF THE INVENTION
This invention relates generally to methods and
apparatus for seismic exploration and more particularly
relates to methods and apparatus for three-dimensional
seismic exploration.
Conventional seismic exploration systems typically
utilize 'llinesl' of sensor groups, each sensor group
composed of one or more individual sensors or geophones,
utilized to obtain seismic data. Often each sensor group
will include from 1-30 geophones electrically intercom
netted to form a single data channel. Conventional
systems utilize a multi-conductor seismic cable containing
many conductor pairs, one pair for each sensor group, to
transmit the seismic data from the sensor groups to a
central processor including multi-channel data processing
and recording capability.
In seismic exploration it is often desirable to
utilize a plurality of these lines of sensor groups so as
to receive the effects of an energy source at variously-
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spaced locations relative to the location of the energy
source. This multi-line operation facilitates three-
dimensional mapping of the geological formations being
surveyed. Existing techniques for mul~i-line operation
have typically involved setting out a plurality of lines,
each line individually coupled to a central control and
recording unit (CCU). This requires a large number of
cables to be strung out over an, often, large geographical
area. This makes not only the initial set up of the
seismic survey system very difficult and costly, but also
makes any subsequent changes in the physical location of
the CCU very difficult.
Additionally, such a system requires a great deal of
manual operation in order to accomplish various objectives
in three-dimensional survey operations, such as shot point
roll and the associated sensor station roll with accom-
paying changes in parameters of stations relative to the
shot point. Further, such systems do not record data in
relation to the shot point locations. Shot point patterns
for such systems are therefore limited by practicalities
of shot point location monitoring.
Accordingly, the present invention provides a method
and apparatus for three-dimensional seismic surveying
whereby a plurality of lines of sensors may be coupled to
a central control and recording unit with a minimum number
of cables and whereby data from sensor arrays, and pane-
meters of such data may, be obtained with optimal
flexibility and be recorded in relation to individual
shot point locations.
SUMMARY OF THE INVENTION
A seismic system in accordance with the disclosed
invention includes a ground electronics having a plurality
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of lines with each line including a plurality of geophon~
arrays arranged at stations along the line. These lines
are then coupled back to a CCU which controls data acquit
session from the geophone arrays. In a particularly
preferred embodiment, groups of geophone arrays are
coupled to control units which serve as interfaces for
signal coupling communication between the CCU and the
geophone arrays. Also in a particularly preferred embody-
mint, each line further includes a signal directing unit
which is responsive to the CCU and which may be utilized
to regulate the operation of the control units and to
receive and process communications between the CCU and the
control unit. These signal directing units are preferably
coupled together in a serial fashion and may be linked
back to CCU by a single link including dual fibrotic
links, each link including two fibrotic conductors.
The seismic survey system of the present invention
utilizes a plurality ox X-Y coordinates to determine the
placement of each active geophone array in the ground
electronics. The system may selectively control these
geophone arrays and may monitor the shot points which
produce the seismic energy which is sensed by these arrays
through reference inditia which the system establishes and
assigns to each signal directing unit, each control unit,
and each sensor array.
Accordingly, the invention in one broad aspect pertains
to a seismic survey system, comprising a plurality of data
lines, a plurality of geophone arrays coupled to each of
the data lines with groups of the geophone arrays being
coupled to control units, and means for selectively
obtaining data from one or more of the geophone arrays, the
means for selectively obtaining data from one or more of
the geophone arrays comprising a central control unit,
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which is adapted to address the control units and further
adapted to receive data from the control units.
Another broad aspect of the invention pertains to
apparatus for conducting multi-line seismic surveying,
comprising a plurality of seismic sensor arrays arranged
in a plurality of survey lines, and means for selectively
controlling parameters of the sensor arrays. The means
for selectively con-trolling parameters of the sensor
arrays comprise a central control unit adapted to generate
command instructions regarding the parameters of the
sensor arrays and means for communicating the command
instructions to the sensor arrays.
Still another broad aspect of the invention comprehends
a seismic survey system comprising a central control
unit, with a plurality of data lines, each date line
having a plurality of geophone arrays coupled thereto.
Means provide for recognizing and addressing each of
the plurality of geophone arrays and means monitor the
location of the seismic energy source in response to
the means for recognizing and addressing the geophone
arrays.
A still further broad aspect of the invention pertains
to a method of seismic surveying, comprising the steps
of establishing a plurality of data lines, each data
line including a plurality of geophone arrays coupled
thereto and further including a plurality of remote data
acquisition units, each of the geophone arrays being
coupled to one of the remote data acquisition units,
and selectively obtaining data from at least a portion
of the plurality, of geophone arrays.
Other aspects and advantages of the invention will
become apparent from the description herein of the preferred
embodiment.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a schematic illustration of a seismic
survey in accordance with the present invention.
Figure lo is an illustration of the CCU shown in
Figure 1, depicted in block diagram form.
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Figure 2 illustrates a fibrotic link as utilized
with a preferred embodiment of the present invention,
depicted in vertical section.
Figure 3 illustrates a connector/transceiver as
utilized to terminate ends of the fibrotic link of
figure 3.
Figure 4 illustrates the photo detector
receiver/amplification circuit of the connector/trans-
sever of Figure 3, depicted in block diagram form.
Figure 5 illustrates the optical transmitter of the
connector/transceiver of Figure 3, depicted in block
diagram form.
.
Figure 6 is a further schematic illustration of both
the photo detector receiver/amplifier of Figure 6 and the
transmitter of Figure 6.
Figure 7 illustrates a remote data acquisition unit
suitable for use with the present invention, depicted in
three-dimensional view.
Figure 8 illustrates the circuitry of the remote data
acquisition unit of Figure 7, depicted in block diagram
form.
Figure 9 illustrates the buzzer alarm logic of Figure
8, depicted in block diagram form.
Figures lo A & B illustrate a single channel of the
quad preamp/filter of Figure 8, depicted in block diagram
form.
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Figure 11 illustrates the switch filter control
circuit of the circuit of Figure 10.
Figure 12 illustrates track and hold, instantaneous
floating point and A to D converter circuitry of Figure 8
depicted in block diagram form.
Figure 13 illustrates mask control logic included
within the timing and control logic circuit of Figure 8.
Figure 14 illustrates the timing and control logic of
Figure 8, depicted in block diagram form.
Figure 15 illustrates box direction/box on line
control of Figure 14, depicted in block diagram form.
Figures 16 A & B illustrate the Manchester II decoder
and serial to parallel converter of Figure 14, depicted in
block diagram form and a timing diagram of the operation
of such circuit.
Figure 17 illustrates box address control circuitry
in block diagram form.
Figures 18 & 19 illustrate HOT detector and HOT
generator of the output formater/encoder circuit of Figure
9.
Figure 20 illustrates the formatter circuit of Figure
8, depicted in block diagram form.
Figure 21 illustrates Manchester II coder of Figure
20, depicted in block diagram form.
Figure 22 illustrates the function generator of
Figure 8, depicted in block diagram form
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Figure 23 illustrates the power supply and battery
pack of Figure 8, depicted in block diagram form.
Figure 24 PA & B) illustrates a signal directing unit
as used in accordance with the present invention, depicted
in three-dimensional and in overhead views.
Figure 25 illustrates the Electronics of the signal
directing unit of Figure 24, depicted in block diagram
form.
Figure 26 illustrates the power supply of Figure 25
in block diagram form.
Figure 27 illustrates common circuitry of the multi-
pled and master control circuit of Figure 25, depicted in
block diagram form.
Figure 28 illustrates box direction control circuitry
of Figure 27, depicted in block diagram form.
Figure I illustrates the command word/data multi-
plexer circuit of Figure 27, depicted in greater detail.
Figure 30 schematically illustrates command word
selector circuitry of Figure 27.
Figure 31 illustrates command word decoder circuitry
of Figure 27, depicted in block diagram form.
Figure 32 illustrates preamble and HOT stripper of
Figure 31 in further block diagram form.
Figure 33 illustrates Manchester II decoder circuitry
of command word decoder of figure 31, depicted in further
block diagram form.
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Figure 34 illustrates the RUT data encoder of Figures
26 and 27, depicted in block diagram form.
Figure 35 illustrates the line steering and HOT
regeneration circuitry of the multiplexer and master
controller circuitry of Figure 25, depicted in block
diagram form.
Figure 36 illustrates LO-side RUT return data restore-
lion circuitry of Figure 25, depicted in block diagram form.
Figure 37 illustrates line steering and HOT regenera-
lion circuitry of Figure 36 in schematic representation.
Figure 38 illustrates OW word restoration circuitry
of Figure 25, depicted in block diagram form.
Figure 39 illustrates a ground electronics grid
system including a shot point shooting pattern.
Figure 40 illustrates the grid system of Figure 38
with a different shooting pattern.
Figure 41 illustrates the grid of Figure 39 with a
schematic depiction for tapered parameters on the geophone
arrays.
Figure 42 illustrates a seismic survey system include
ivy both standard and alternate geophone arrays and a
schematic representation of their usage in accordance with
the present invention.
Figure 43 illustrates a flow chart for setting up a
system in accordance with the present invention.
I
Figure 44 (A & B) illustrates a flow chart for
establishing operating parameters for a system in accordance
with the present invention.
Figure 45 (A, B & C) illustrates a flow chart indicating
one means in accordance with the present invention for
incrementally keeping track of the shot point and data
recording channels as the shot point advances.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT
Referring now to the drawings in more detail, and
particularly to Figure l, therein is schematically thus-
treated a seismic survey system lo in accordance with the
present invention. Seismic survey system lo includes CCU
12 which will typically and preferably be located in a
truck or similar readily movably unit. CCU I is
coupled, preferably by a single fiber optic link 14 to a
first recorder takeout unit (RUT) AYE which is then, in a
multi-line configuration, serially connected to add-
tonal, preferably identical RTUIs 16.
Each seismic line 20 includes one or more remote data
acquisition and control units (Ruts) 22 which are prefer-
ably coupled by fiber optic links to an RUT 16 for that
line or to other Ruts 22, if multiple Ruts 22 are present
in the line. These fiber optic links also include a
plurality of twisted pair conductors individually coupled
to a plurality of takeouts 24 for connecting a plurality
of geophone arrays I
Fiber optic links 14, lo are terminated at each end
by a connector/transceiver 18. Each of these connect
tor/transceivers 18 contains optical receiver and optical
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transmitter circuitry for appropriately converting signals from electrical to optical or from optical to electrical.
Each RUT 22 contains the necessary circuitry to
preamplify, filter, gain range, and digitize the analog
signals from the geophone groups 26.
Ruts 16 serve as an interface between lines 20
connected thereto and CCU 12. Each RUT 16 contains
circuitry to regenerate the code transmitted between CCU
12 and the Ruts 22. Additionally, Ruts 16 facilitate the
addressing of any desired line by CCU 12.
In general, the operation of a system as depicted in
Figure 1 is as follows. Communication from CCU 12 to
ground electronics 13, composed of lines 20 with Rut 22
and Ruts 16 is achieved by use of command words (Cows).
The Cows are transmitted continuously and sequentially at a
predetermined rate. The Cows provide instruction and
sample acquisition commands to the ground electronics.
Following each OW is a command called END OF TRANSMISSION
(ETA.
Ground electronics 13 is divided into two sides, high
side 15 (to the right of vertical dotted line 21~ and LO
side 17 (to the left of the vertical dotted line 21).
Each side is commanded simultaneously by Cows communicated
across optical link 14 to Ruts 16. Each RUT 22 receives
and controls signals from a different group 27 of geophone
arrays 26 through cables 19.
Taking, for example, LO side 17 of ground electronics
13, when RUT aye receives the OW and HOT, RUT aye passes
the OW on to the next RUT in this case, aye, and to the
next RUT, in this case, 16b. The HOT is similarly passed
on to RUT aye, but it blocked from transmission to RUT 16b.
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When RUT aye receives the OW, it both passes the OW on to
RUT 16b~ and, acquires a sample on all channels, each
channel assigned to an individual geophone array 26 in
group 27. RUT aye receives analog samples from geophone
S arrays 26 and converts the samples into digital data and
stores such data in memory. RUT 22b also prepares to
receive an HOT and becomes ready to transmit acquired data
to CCU 12.
When RUT aye receives the HOT, it blocs the HOT from
being retransmitted to the next RUT in this example 22d,
and begins transmission of the previous acquired sample
data to CCU 12. When the transmission of this data is
complete, RUT aye will generate an HOT and transmit it to
RUT 22b. The same process will then be repeated with RUT
22b as well as all other Rut on line LO side 17 of line
aye.
RUT aye will independently be monitoring data trays-
milted by Rut aye, 22b, and any other Rut on LO side 17 online aye. When data from these Rut stops, signifying that
all data from LO side 17 of line aye has been transmitted,
RUT aye will transmit a status signal to CCU 12. After
the status signal has been transmitted, RUT aye will
generate an HOT and transmit it to RUT 16b which will then
pass the HOT on to RUT 22c and repeat the same process on
line 20b as was carried out on line aye. This sequence
may be repeated through a number of Ruts 16 and Rut 22
over a desired number of lines 20, principally limited
only by channel handling capacity of CCU 12 to accommodate
data from each sensor station.
This same procedure is simultaneously being carried
out on the high side of each line by circuitry in the same
Ruts 16 and by the associated Rut 22 on high side 15 of
ground electronics 13.
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Referring now to Figure 2, therein is illustrated in
vertical section a dual duplex fiber optic link I of the
type preferably utilized to couple CCU 12 to RTU1s 16. It
is to be clearly understood that for sake of convenience,
all fiber optic links 14, 19 may foe of this type, though
in the illustrated embodiment, such links will not be
utilized to their full capacity or to equal capacities in
all placements.
Link 14 includes a jacket 32 preferably constructed
of polyurethane, which surrounds four optical fibers 34.
A buffer tube 36 surrounds each optical fiber 34 to aid in
preventing optical fibers 34 from being damaged when they
are looped or otherwise bent. A strength member 36
extends through the center of link 14. Strength member 36
may be a Cavalier fiber, an Armed fiber, a high tensile
strength plastic fiber or the like and is provided to
relieve tension from the fibers when external forces are
applied to the link. Six twisted pairs 38 of wiry are
also included within link 14 to facilitate usage as link
19 with takeouts for geophone arrays 26 or for use as
wire lines for communication equipment.
Referring now to Figure lay therein is illustrated
CCU 12, depicted in block diagram form. CCU 12 contains
the necessary equipment to control ground electronics 13
and to receive and retain data therefrom. Those skilled
in the art will recognize that the configuration of
central control unit 12 may take many forms and that the
described embodiment is merely illustrative of one of
these forms.
Input panel 29 physically couples to
connector/transceivers 18 to provide communication between
CCU 12 and fiber optic cable 14. Input panel 29 contain
signal processing circuitry to reconstitute data received
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from ground electronics 13. Input panel also contains
decoying circuitry suitable for decoding the encoded data
from ground electronics 13 prior to transmitting the data
to system controller 31. A similar decoding operation
will be discussed in more detail later herein, in relation
to operation of the Ruts 22.
Remote front end (RYE) 33 is a microprocessor-based
controller which serves as an interface between ground
electronics 13 and system controller 31. RYE 33 includes
suitable controls to allow an operator to interface with
the system. In a particularly preferred embodiment, the
I is based upon a Model TMS-9900 microprocessor as
manufactured by Texas Instruments Inc. RYE 33 allows the
operator to control multi-line operation of seismic
exploration system 10, including the selection of
operating parameters such as tapered lines (varied gap,
preamplifier gain, and geophone source array patterns) as
will be discussed in more detail later herein. RYE 33
also contains appropriate circuitry to interface the
operations of ground electronics 13 with one or more
sources of seismic energy 39. This interface may be
accomplished in a generally conventional manner known to
the industry.
System controller 31 controls the various data
manipulation functions to handle data compilation and
retention. System controller 31 also serves as an
electronic interface to all peripheral devices, such as
mass memory 35, and tape transport 37. System controller
31 is also preferably a microprocessor based system which,
at a particularly preferred embodiment, is also based upon
the Model TAMS g900 microprocessor manufactured by Texas
Instruments Inc. Operator inputs are provided to system
controller 31 to allow an operator to issue commands to
the peripheral devices attached to the system. For
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example, associated with system controller 31 in a
preferred embodiment is a mass memory 35 has a capacity of
3.g megawords. More than one mass memory may be utilized
to facilitate the recording in a greater number of data
channels or to facilitate various types of data monopoly-
lion by system controller 31, such as "stacking of data"
as is well known in the art. System controller 31 also
preferably communicates with a data recording medium such
as tape transport 37 which is utilized to retain the data.
System controller 31 will also generate timing and control
signals for synchronization of system functions.
Referring now to Figure 3, therein is illustrated a
fiber optic connector/transceiver 18 of the type prefer-
ably utilized to make all connections wherein a dual duplex fiber optic link as shown in Figure 2, is utilized.
Connector/transceiver 18 has a shell or cover 42
which attaches to a mounting member 44. rubber gasket
16 is provided to form an environmental seal between
mounting member 44 and cover 42.
A hollow rectangular member 48 is secured to mounting
member 44 for receiving one end of a fiber-optic link 14.
Members 44 and 48 may be a single integral piece. Link 14
extends through a gland 49 which is connected to one end
of rectangular member 48 by a nut 54 so as to seal around
link 14.
The six twisted pair wires 38 in link 14 are soldered
or otherwise connected to pin connectors of an electrical
connector or plug 50, which is secured to mounting member
44 at the end opposite rectangular member 48. Electrical
connector 50 may be of any conventional, environmentally
suitable type.
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Two optical fibers aye, 34b of lynx 14 are terminated
in fiber optic transmitter modules aye, 64b through fiber
optic connectors 66. Fiber-optic connectors 66 may be of
any conventional type, such as an Am phenol SPA series
connectors. Optical transmitter modules 64 may be of any
conventional type such as a model no. SPY 4140 manufac
lured by Spectronics.
The remaining optical fibers 34c end 34d are term-
noted through respective fiber optic connectors 66 unconventional optical detectors aye and 68b. Both optical
detectors aye and 68b and optical transmitters aye and 64b
are mounted on printed circuit board assemblies (Pubs) 70,
which are secured to mounting member I Pubs 70 contain
circuitry which activates the transceivers as will be
discussed more fully herein below with respect to Figures
4 and 5. Pubs 70 are connected to plug 50 such as by a
plurality of wires (not illustrated).
When assembled, connector/transceiver 18 provides an
environmentally sealed optical cable connector which
protects the transceiver and the ends of the optical
fibers from being affected or damaged during field use.
Connector/transceivers 18 are readily connectable to Rut
25 22, Ruts 16, or CCU 12 via plug 50. lever or wrench 72
affixed to plug 50 enables connector/transceiver 18 to be
locked into place when secured to a compatible, comply-
Monterey connector.
Referring now to Figure 4, therein is illustrated an
electrical block diagram of the photodetector receiver/
amplification circuit 80 of connector/transceiver 18.
Optical fiber 34 is coupled to fiber optic detector 82
which converts the light pulses to differential electrical
output pulses of opposite amplitudes. These pulses are
coupled into amplifier 84 which preferably includes
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successive differential amplifier stages until a suffix
client level is reached for logic compatibility. Amplifier
I is provided with a hysteresis circuit 86 which provides
a generally square wave pulse output from amplifier 84.
Bias and symmetry restoration circuit 88 and comparator 90
are provided to assure a square wave output and to adjust
the signals for proper compatibility for transistor-to-
transistor logic (TTL) circuitry. Because
receiver/amplification circuit 80 is AC coupled, it can
power up in either logic state. A hold off circuit 92 is
provided to assure that the receiver always powers up in a
single (Lo) logic state.
Referring now to Figure 5, therein is illustrated
optical transmitter 94. An LED driver 96 and an LED I
are provided. LED 98 is optically coupled to optical
fiber 34 such that the light which is emitted by LED 98
whenever driver 96 goes to a high logic state is trays-
milted over optical fiber 34. In Figure 6, photodetector
receiver/amplification circuit 80 and optical transmitter
94 are shown in further schematic form.
Referring now to Figure 7, therein is illustrated in
three-dimensional view an RUT 22 as depicted schematically
in Figure 1. RUT 22 includes a box 132 containing elect
ironic circuitry as will be described more fully later
herein. RUT 22 includes a detachable DC power supply or
battery pack 142 for powering the electronics within box
].32 and within connectors/transceivers 18 which are
connected to box 132. Two connectors 144, mutable with
connectors 50 on connector/transceivers 18 are provided on
box 132. An additional two correctors 145 are provided as
alternate connections for geophone arrays (26 in figure
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1). Rather than connecting geophone arrays 26 to takeouts
136 in links 18, geophone arrays 26 may be connected
directly to remote units 22 through connectors 145 if
desired.
Referring now to Figure I, therein is shown the
circuitry of an RUT 22, depicted in block diagram form. As
shown, eight analog inputs, four from each of two standard
connectors 144 or alternate connectors 145, are fed over
lines 150 to multiplexer 152, which selects either stank
dart or alternate inputs. The analog inputs are both
filtered for high frequency and amplified in quad primps
154 prior to being input into track-and-hold, instant
Tunis floating point (IMP), and analog-to-digital (A/D)
module 156. All analog input signals are sampled Somali-
tonsil by the track and hold network, and are gain-
ranged from 1 to 32,768 times to near A/D mid scale by the
IMP, as disclosed in U.S. Patent Nos. 4,104,596 and
4,158,819, which are incorporated herein by reference.
The resulting digitized mantissa and gain words for each
original input or channel are fed to output formatter 158,
which loads the parallel data into a serial output buffer
for transmission via optical link 14 to CCU 12.
Timing and control logic unit 160 functions as a
controller for RUT 22. It receives and decodes control
data from CCU 12 through receivers 162 to initiate the
sampling and digitization process. All channels are
sampled simultaneously, gain-ranged, and digitized accord-
in to the control logic sequence. At the appropriate
time, the timing and control logic provides digital data
to transmitters 164 for transmission to CCU 12. Control
pulses received from CCU 12 contain an operation code, a
group of five bits which the timing and control unit
decodes into remote unit setup parameters, such as
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standard/alternate sensor relay selection, K gain, filter
selection, function generator control, etc.
Power supply board 166 utilizes battery pack 142 to
develop regulated voltage supplies via DC-to-DC con-
venters. Power on/off interlock 168 is provided to enable
remote unit power-up and operation when one or more cable
connectors 10 are engaged, as discussed more fully below.
Buzzer 167 is provided primarily for theft protection,
however, it also provides indication of faulty operating
conditions.
Shown in Figure 9 is the logic for buzzer alarm 167.
Signal CONNECTORS ON is generated when either of the two
connector/transceivers is attached to remote unit 22. The
signal CONNECTORS ON clocks one-shot 300 which momentarily
activates the buzzer, indicating that battery pack 142 is
not dead. Unauthorized disconnect register 302 and
unauthorized POWER DOWN register 304 are enabled whenever
the RUT is powered up. The reset of these registers is
controlled by CCU 12. When both connectors are removed,
signal CONNECTORS OFF goes HI, AND-gate 306 is triggered,
thereby energizing the buzzer. This theft protection is
operable with the RUT powered up or powered down. When
communication to CCU 12 is interrupted, signal POWER DOWN
goes HI. If unauthorized POWER DOWN register 304 is set
when signal POWER DOWN goes HI, flip-flop 308 and AND-gate
310 are activated, thereby energizing the buzzer. Buzzer
67 may also be enabled by an external voltage check
circuit (not illustrated).
Referring now to Figures AYE and 10B, therein is
shown a bock diagram of a single channel of quad
preamp/filter 154. when test relay 170 is enabled to the
external inputs position (as shown), geophone analog input
signals are fed into primp or K Gain stage 172. K Gain
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stage 172 may be remotely programmed to gains of 4, 16,
64, or 256 by register 174. Low-cut refilter 176
receives the output from primp 172 and serves to Low-pass
filter the signal prior to its input into switched Low-cut
filter 178. Low-cut filter 17~ may be configured as an 0
(OUT), 12, 24, or 36 dub per octave high-pass filter by
proper stage selection with switches 180 and 182, which
are set by register 184. Low-cut corner frequency is
determined by the duty cycle of low-cut frequency clocks
186, as more fully discussed below in connection with
Figure 12.
Low-cut filter 178 is followed by 50 or 60 Ho strap-
pale notch filter 188 which is remotely selectable as
either 'fin" or "out" with switch 190. Notch filter 188
consists of two cascaded, stagger-tuned, second order
notch filters to provide better than 60 dub attenuation
over a 0.2 I bandwidth.
Seventh order switched elliptical anti-aliasing
filter 192 follows notch filter 188. The corner frequency
is remotely selected by the duty cycle of alias frequency
clock 194, as discussed more fully below in connection
with Figure 10, at one of sixteen frequencies between 39
to 500 Ho. The preferred slope in this frequency range is
96 dB/octave MAX. it will be clearly understood that
these parameters are exemplary only and that other
parameters may be utilized.
Anti-aliasing filter 192 is followed by post-aliasing
filter 196 which removes switching transients from the
signal. The output of filter 196 is AC-coupled into gain
stage 198 which functions as an output buffer and gain-
adjust mechanism. The output is then switched to the
35 track-and-hold (Figure 11) by control logic 222 using
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switch 200. Low-cut filter 178 and anti-aliasing filter
192 use pulse width controlled signals for controlling
filter corner frequencies.
Shown in Figure 11 is a schematic diagram of the
switched filter control circuit 232 which venerates the
necessary clock pulses and provides the CCU interface for
pulse width control. This circuit also synchronizes the
filter switching with the control clock, thereby minimize
in the transient signal noise received by the track-and-
hold.
Clock circuit 312 divides a megahertz signal to
generate a 512 KHz or 256 KHz clock signal, depending on
whether anti-alias filter 192 corner frequency is set
above or below 250 Ho (by OW data). The clock signal is
divided by 64 in counter 314 to yield an 8 KHz or 4 KHz
period for filter control. The 8 KHz/~ KHz signal is used
as a reset signal for counters 316 and 318 and latches 320
and 322. Counters 316 and 318 control the pulse width of
the filter control signals by setting latches 320 and 322,
respectively, at a time determined by OW data. The end
result is that the filter switching control period is
controlled by the anti-alias corner frequency which
selects either an 8 KHz or 4 KHz reset cycle. The pulse
widths of the filter control signals, which correspond to
the respective duty cycles, are determined by the values
loaded into registers 324 and 326 (which preset counters
316 and 318, respectively) by a OW over line 328 from CCU
12.
In the presently preferred embodiment, -there are four
preamps/filters per canal, along with associated data
registers and support circuitry. Two quad primp cards
154 are provided in each box 132; however, control logic
160 can accommodate a single card.
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Figure 12 is a block diagram of trac~-and-hold, IMP,
and A/D module 156 of Figure 8. Each primp (154 in out-
put is fed into a corresponding track-and-hold (T/H)
aye (a total of eight) prior to reception of a OW
from CCU 12. When the command is detected, T/H aye
are simultaneously switched from the tracking mode to the
hold mode, thereby providing minimum sampling skew.
According to the established box direction and
sampling rate, successive channels are multiplexed by MIX
switch 206 to IMP gain-ranging amplifier 208. MU control
is provided by channel address counter 210. The basic
purpose of IMP amplifier 208 is to amplify the analog
input signals to a value near the full-scale range of A/D
convertor 212, usually between one-half and full scale,
and to provide a digital code corresponding to the actual
gain applied to the input signal.
The signal is held constant during the gain-ranging
process. This process uses a successive approximation
logic sequence to apply appropriate IMP gain stages 20S to
amplify the hold sample by the necessary gain on, where n
= o, 1, 2,..., 15. Level detector 214 is enabled at the
end of each IMP gain stage time cycle. The amplified
signal is then sampled by A/D track-and-hold 216 and
converted to digital data by A/D converter 212 for trays-
mission along with the gain code generated during the
gain-ranging process.
To prevent various stages of IMP amplifier 208 from
introducing significant offset errors, a correction
voltage is subtracted from each stage. Periodically, the
offset of each IMP stage is detected by offset logic 218,
and the correction voltage is incremented by a small
amount in a direction that will reduce the offset.
Jo us
-21-
MU average 220 it used to correct primp offset
errors prior to gain stage amplification. Each channel's
error correction voltage is summed into its held signal to
cancel the offset during its MU time. The correction
signals are updated each scan time.
Control logic 222 provides the timing and control for
T/H, IMP, and A/D module 156. This logic controls the T/H
MU timing, IMP gain stage switching, A/D converting, and
data register storing.
System size is input from RUT timing and control logic
(160 in Figure 8) to channel address counter 210. Four or
eight channels are selected, based on the desired field
spread and scan rate. When channel selection other than
four or eight is required, data is still multiplexed to
IMP amplifier 208 as four or eight channels, but unneces-
spry data is stripped before transmission to link 14 by
the output formatter (158 in Figure 8).
As shown in Figure 13, mask control logic 329 which
is included in timing and control logic 160, controls the
digitized analog data to be formatted and transmitted to
CCU 12. Control is achieved by CCU 12 loading a mast bit
for each channel, which enables the selection of specific
channels for data input to the CCU 12. Two 8-bit aegis-
lens 330 and 332 are provided so that dynamic sampling may
be achieved. As only one register is used at a time, the
other register may receive updated mask bits. The transit
lion between registers 330 and 332 is controlled by CCU12.
Each analog channel is dedicated to a particular
geophone group, and one of eight different MU address
codes 000, 001, 010, ..., 111 is dedicated to each
channel. Whenever data is available from any one channel,
~23'~ 5
-22-
its address code is presented to multiplexer 334. Multi-
plexer 334 selects the corresponding mask bit for that
channel and presents it to the output formatter ~158 in
Figures 8 and 14~. A "1" mask bit allows the formatter to
convert channel data for transmission; a "O" causes the
formatter to ignore this channel.
Referring to Figure 14, therein is shown a block
diagram ox remote unit timing and control logic (160 in
Figure 8). Box "power on" control interlock 1~8 cycles
power to the optical receivers (80 in Figure 5) in
connector/transceivers 18 until transmission is detected,
at which time the main RUT power supply (166 in Figure 8)
is enabled. If no optical reception occurs for a specie
fled period of time, "power on" circuitry 168 senses the inactivity and returns to the cyclic power on/off mode.
Because connector/transceivers 18 are mechanically
identical, box direction/box on line control circuit 224
is provided. Circuit 224 determines the direction of
incidence of the first communed signal and establishes
this as the CCU direction. With this information, the RUT
may be set up for proper primp multiplexing regardless of
connector interchange.
Referring now to Figure 15, therein is illustrated in
greater detail box direction/box on line control 224 of
Figure 14. Each powered-up RUT begins in a repeater mode.
After a OW transmitted by CCU 12 passes through a remote
unit 22, signal OW RECEIVED clocks box-on-line flip-flop
336, which switches out receiver lines 338 and connects RUT
data formatter/encoder 158 and end-of-transmission (HOT)
generator (230 in Figure 14) to the appropriate optical
transmitters. The RUT has now been taken out of the
repeater mode and is awaiting receipt of the HOT signal
from the previous upstream RUT after detecting this HOT
I
-23-
signal (which is blocked from passing through to the next
RUT), RUT 22 transmits its encoded data upstream to CCU 12.
Thus, the data from this RUT is inserted behind the data
from the previous RUT By controlling when the HOT is
transmitted from the previous RUT the gap between the two
data bursts is controlled.
.
After the encoded data has been transmitted to CCU
12, the RUT transmits an HOT signal to the next downstream
RUT At this time, signal DATA TRANSMITTED clocks flip flop
336, which disconnects formatter/encoder 158 and HOT
generator 230 and places remote unit 22 back in the
repeater mode.
To ensure that the entire OW has been received by the
RUT the RUT remains in the repeater mode for a time period
of preferably nine microseconds after signal OW RECEIVED
is generated. This time period is longer than the time
required to receive a OW, jut shorter than the time lag
between the generation of signal OW RECEIVED and the HOT
signal.
Referring again to Figure 14, Manchester II decoder
and serial-to-parallel conversion logic 226 functions as
an input decoder and data formatter. Manchester II code
(Man II code) is utilized because of its "self-clocking"
asynchronous format. All transmissions are burst mode Man
II code to conserve power. As shown in Figures AYE and
16B, decoder and serial-to-parallel logic circuitry 226
decodes the incoming signal and stores it in a parallel
register for output to OW decoder 22~. As shown, a
Manchester II clock pulse (Man II ok) is generated by
EXCLUSIVE OR-gate 340 and inventor 342 each time a transit
lion occurs in the Man II code. The Man II ok clocks
one-shot 344 which has a time constant of 3/4 bit cell
time. The Man I ok also clocks J/K flip-flop 346, with
~23~
-24-
the 3/4 bit cell time tied to the J input. The Q output
of flip-flop 346 is Manchester II data representative of
either seismic data being transmitted upstream or command
data being transmitted downstream). If a Man II ok occurs
during the 3/4 bit cell time, the Q output of flip-flop
340 goes IT indicating that the Jan II data is a "1".
The 3/4 bit cell time also clocks the Man II data into
33-bit serial-to-parallel shift register 348. If a Man II
ok occurs during the 3/4 cell time, a "1" is loaded into
register 348. Otherwise, a "O" is clocked into register
34~3.
A preamble of all zeros precedes a OW. As a result
of repeated transmission, the leading bits of the preamble
may become distorted and decoded as a "1". To prevent
false l's from being detected, preamble stripper logic SO
is utilized. When the preamble is received, the first
transition of Man II code causes flip-flop 352 to go HI.
This HI output is delayed by strip time ARC time constant
circuit 354, preferably established at two microseconds.
After the time delay, one-shot 344 is allowed to fire.
Flip-flop 352 is reset after all OW data is received.
This OW data includes:
1. Preamble - a 24 to 56 bit all "O's" data train
used by optical receiver symmetry restoration
circuitry 124 (Figure 4 to maintain input data
integrity. RUT Logic effectively ignores this
segment of the OW;
2. Sync Code - a two-bit sequence signifying
decoder start;
~;~3~f~5
-25 -
3. RUT Address - a nine-bit code unique to each RUT
RUT logic ignores all codes except all "l's" and
its box address. Addresses are assigned during
the RUT power-up sequence;
4. OX Code - a five-bit code defining the operation
to be performed. For example, a box address
assignment has Ox Code OWE;
5. Data Word - a fifteen-bit code which is loaded
into registers for primp control box set-up
(mask), function generator, etc.;
6. Stop Bit - a one-bit code, a "1" used as a data
validity check bit, indicates that the data is
good;
7. Delay - a calculated N bit data delay which
allows each RUT to dump its data onto the optical
JO link before receiving additional data from the
adjacent RUT and
8. HOT - a four-bit code which signifies end-of
transmission of the OW and the start of data
output to the CCU.
As stated above, the OW includes a nine-bit code
which is used to give each RUT an individual identity in
order to keep its data separate. As shown in Figure 17,
nine-bit register 374 is provided in each RUT affording
512 possible different combinations. Comparator 376 is
included to identify any OW box address that matches the
data in register 374. All l's detector 378 is provided to
detect an all l's address code.
I
-26-
When the RUT powers up, register 374 it cleared so
that the box address is "one. A special OW trueness
muted by the CCU assigns a binary number between one and
510 to the RUT as determined by the relative position of
this RUT with respect to CCU 12 and the other Rut 22, which
is loaded into register 374. The numbers one through 510
are used as individual box addresses. An all zeros
address code is used only during powering up, while an all
l's code is used to enable CCU 12 to communicate with all
of the Rut at the same time.
Referring again to Figure 14, end-of-transmission
detector generator 230 determines when an HOT code is sent
to the next RUT so the latter can transmit it data. As
shown in Figures 18 and 19/ two individual HOT circuits
control the transmission of data from the Rust One
detects the HOT transmitted from the previous upstream RUT
the second general s an HOT code for transmission to the
next downstream RUT
The HOT detector of Figure 18 includes counter 366
which is reset and enabled when a OW is received. Counter
366 is disabled after the HOT code is received. The OW
precedes the HOT code in the data stream. The time delay
between them depends on the quantity of data transmitted
by each RUT and the position of the particular RUT in the
line. The more Rut between this RUT and the CCU, the
longer the delay between the OW and the HOT. The HOT code
clocks counter 366, thereby triggering the
formatter/encoder (15B in Figure 8) to begin data
transmission.
The HOT generator of Figure 19 is partially con-
trolled by CCU 12. Typically, HOT transmission is come
pleated approximately one microsecond after data trays-
mission is completed. CCU 12 can change this time differ-
~23
-27~
entail or gap by modifying the code loaded into register
358. A different code addresses another section of
programmable read-only memory (PROM) 360, producing a
different HOT position with respect to transmitted data
(that is, changing the gap). Counter 362 counts the
number of digitized analog channels which are to be trueness
milted. Counter 362 addresses PROM 360, and the output of
PROM 360 presets counter 364. As data is transmitted,
counter 362 begins counting, and the output from counter
362 allows the HOT code to be transmitted at the correct
time.
Primp control logic (232 in Figure 14~ determines
the frequencies and duty cycles of the lookout and anti-
alias switched filter clocks 186 and 194 (Figure lo and decodes and enables all other primp setup and control
functions defined in the primp block diagram (Figure lo.
Figure 20 is a block diagram of the output
formatter/encoder (158 in Figure 8). In the presently
preferred embodiment, a standard set of output data for
each channel includes a four-bit Cain word and a fifteen-
bit data word. Output data from each RUT is formatted into
a sequence of words as follows: (l) a two-bit sync code;
(2) a one-bit box fault code; (3) a nine-bit RUT address;
and (4) one to eight sets of channel data. The total word
length is selected to obtain a "O" logic level at the end
of transmission to conserve power between transmissions
and to utilize eight-bit groups to simplify encoding. The
hollowing chart indicates the nine possible word lengths
which may be transmitted from a RUT 22, depending upon the
number of channels being transmitted:
-28-
NO. Of BITS
OUTPUT DATA TRANSMITTED
SYNC + FAULT + ADDRESS O CHANNELS = 12 BITS 16
SYNC FAULT + ADDRESS + 1 CHANNEL = 31 BITS 32
SYNC + FAULT ADDRESS 2 CHANNELS = 50 BITS 56
SYNC FAULT + ADDRESS 3 CHANNELS = 69 BITS 72
SYNC + FAULT ADDRESS + 4 CHANNELS = 88 BITS 88
SYNC FOLIATE ADDRESS + 5 CHANNELS = 107 BITS 112
10 SYNC FAULT ADDRESS + 6 CHANNELS = 126 BITS 128
SYNC + FAULT ADDRESS 7 CHANNELS = 145 BITS 152
SYNC + FAULT + ADDRESS 8 CHANNELS = 164 BITS 168
It is to be understood that the data output may have other
formats and still remain within the scope of the present
invention.
As shown in Figure 20, the formatter circuit includes
counter 380 to count the number of channels formatted,
PROM 38 to determine how many bits need to be shifted
(based on the above chart), counter 384 to count how many
shifts have occurred, and first-in, first-out (FIFE
memories 386 to store the formatted data until trays-
mission. When the OW is received, the sync bits, fault
bits, and box address are loaded into shift register 388.
Simultaneously, the required number of bits to be trays-
milted are transferred from PROM 382 to counter 384. As
shift register 388 shifts, counter 3~34 counts. After
eight bits are shifted and presented to memory 386, a
clock is generated to load the eight bits into memory.
This process continues until all full eight-bit words are
transferred into FIFO memory, a-t which time counter 380
increments its count. Any left-over bits remaining in the
shift register are used to complete the next eight-bit
word. Two FIFO memories are provided so that one may be
loaded with new data as the other is unloading data to the
encoder circuit.
of
-29-
Encoder circuit 387 generates the preamble, accepts
and serializes eight-bit words from memories 386, and
converts this serial data to Manchester II code. When an
HOT code is received from the previous RUT a preamble of
S specified length (similar to the OW preamble) is goner-
axed, after which an eight-bit data word from memories 386
is transferred to shift register 390. The first word
transferred is the sync bits, the fault bit, and part of
the box address. Register 390 shifts at an 8 MHz rate
into Man II coder 392 which generates the bit cell transit
lions. FIFO memories 386 unload at a 1 MXz rate which
matches the 8 MY shift rate so that there is a continuous
data stream out of Man II coder 392. Encoding stops when
a signal from FIFO memory indicates it is empty. The
final bit coded causes the output of Man II coder 392 to
be at a logic LO level.
Referring now to Figure 21, Man II coder 392 is
enabled by taking the input to AND-gate 394 HI. During
generation of the preamble, register 390 is cleared,
causing all zeros data to be presented to coder 392. OR-
gate 396 causes J/K flip-flop 398 to toggle at bit cell
times. Once generation of the preamble is completed,
memory data is loaded into register 390. As the data
shifts out, flip-flop 398 either changes state at mid-cell
time when a "1" is presented to coder 392 or remains in
its present state because a "0" is presented. After all
data is coded, Man II coder is disabled by taking the
input to AND-gate 394 LO.
Referring now to Figure 22, therein is shown a block
diagram of the function generator (169 in Figure 8). Test
signals are generated simple by sample in digital form by
CCU 12. This digital signal is then transmitted to the
Rut as a part of the OW. In the Rust the digital signal
is converted to an analog signal with a near full-scale
1~3'~'~2~
-30-
peak value by digital-to-analog (D/A) converter 240. Thy
resulting analog signal is attenuated to the desired
amplitude by digitally controlled attenuators 242 and 244.
The LO level analog signal is then fed into primp oscil-
later inputs 201 for test purposes.
Figure 23 is a block diagram of the battery pack and power supply 142 and 166, respectively, in Figure 8.
Battery pack 142 includes two 12 volt lead-acid batteries
connected in series with a common o~tpu~. When a con-
nector/transceiver 18 is engaged with a remote unit
connector 144, interlock circuitry (168 in Figure 8) is
enabled. Optical receivers 92 are cycled on and off to
conserve power until light transmission is detected.
Signal GREG EN then goes HI to force power on/off control
246 to enable soft-start circuitry 248 and main power
relay 250. Power is distributed to two DC-to-DC con-
venters 252 and 254. Resulting outputs are filtered with
high-cut filters 256, 258, and 260 prior to distribution
for various box functions. Secondary relay 262 must be
thrown to enable power to the function generator (169 in
Figure 8).
Referring now to Figures 24 A and B of the drawings,
therein is shown in three-dimensional view a RUT 16 in
accordance with the present invention. RUT 16, like RUT 22
includes a box 700 suitable for protecting the electronics
contained therein from the environment. Box 700 includes
four connectors 702, each of which is mutable with plug 50
on connector/transceiver 18. Two of connectors 702 are
designated as command parts Of and C2 and are utilized for
coupling to the CCU or to other Ruts. The remaining two
connectors are each ports to the HI and LO sides of -the
line in which the RUT is placed.
I 5
-31-
Referring no to Figure 25, therein is shown the
electronics within RUT 16, depicted in block diagram form.
Connector/transceivers 18 are depicted to indicate signal
inputs/outputs to CCU 12 and to a serially connected RUT
(at Of and C2~ and between RUT 15 and adjacent Ruts 22
(labeled "HI" and "Lo"). Two OW carrying optical fibers
aye, 710b, and two return data optical fibers aye and
712b are coupled through connector/transceivers 18 at Of
and C2, and circuitry connected thereto, to Quiddity multi-
plexer and master control circuit 714. Multiplexer bandmaster control circuit 714 includes circuitry which
controls both the common functions of RUT 16, i.e., those
functions related to the Ruts power regulation and data
handling functions, as well as portions of both L0-side
and HI-side system control functions such as signal
steering controls. Multiplexer and master control circuit
714 is then coupled to Lucid control electronic 716 and
HI-side control electronics 71~3, each of which 716 or 718
is dedicated solely to signal handling for its designated
side of the line in which RUT 16 is placed. RUT 16
includes a power supply 720 which is controlled by power
on off control 722. Multiplexer and master control 714 is
also coupled to common OW decoder 724 and common RUT data
encoder 726 which facilitates the response of the RUT to
command signals from the CCU.
Referring now to Figure 26, therein is illustrated
power supply 720 of RUT electronics 700 in greater detail.
A battery pack (not illustrated) such as that previously
described with respect to RUT 16 is coupled through relays
730 for each of the common, HI, and Lo circuitry to DC-
to-DC converters 734 to provide plus and minus 5 volts to
each of HI-side logic and L0-side logic and provide plus
and minus 12 volts and plus 5 volts to common logic.
-32-
Referring again to Figure 25 a soft start circuit 731
is provided, as in the Rust to supply power to the con-
teats of relays 730 to prevent current surges upon relay
operation which might damage the relays. Voltage fault
detect circuitry 733 generates a fault bit if the battery
pack (not illustrated) becomes discharged. This vault
bit is then communicated to RUT data encoder 726 for
transmission to the CCU in the RUT status signal. Control
of power supply 720 comes from power on-off control
circuit 722. When a connector/transceiver 18 is connected
to control port Of or C2, the battery (not illustrated) is
jumper Ed to create an INTERLOCK signal. This INTERLOCK
enables power on-off control circuit 722 to power con-
nector/transceivers 18 at controls Of and C2 on a cyclical
basis; for example, in one preferred embodiment, I Millie
seconds on, 250 milliseconds off, until a valid OW signal
is received. Upon receipt of an appropriate OW, power
on-off control circuit 722 then supplies power on signals
to power supply 720 enabling power to the COMMON and
designated HI and/or LO sides. During operation of the
RUT, power on/off control circuit 722 monitors the LO and
HI-side OW and, upon cessation of a OW to either side, an
automatic POWER DOWN signal is enabled to that side.
Referring now to Figure 27, therein is illustrated
common circuitry of multiplexer and master control circuit
714 in further block diagram form as well as common OW
decoder 724 and common RUT data encoder 726. Fiber optic
OW lines aye and 710b from Of and fiber optic OW lines
coupled to C2 are coupled directly to both box direction
control circuitry 740 and OW data multiplexer circuitry
742. Box direction control circuitry 740 is utilized to
orient the RUT within the ground system; i.e., to
determine which command port will be designated as Of,
linked to the CCU. The OW selector 744 receives OW input
:~L23~25
-33-
signals from the CCU. The signal then passes to OW
decoder 724 where the OW is interpreted and transmitted to
opaqued logic 728.
Box direction control circuitry 740 is shown in more
detail in Figure 28. Box direction control 740 recognizes
the connector/transceiver 18 from which the first OW is
received and designates that connector as C1, i.e., the
connector/transceiver 18 of the link coupled directly to
the CCU. A logic level indicating the connector to be
designated as the control port is then communicated to
Quiddity multiplexer circuit 742 illustrated in Figure 29.
Quiddity multiplexer 742 then appropriately routes signals.
Between each command port fiber optic receiver line and
the appropriate data restoration circuit (715 or 717 in
Figure 25) and between LO-side steering logic for RUT LO,
ROD and RUT LO COWS and transmitter to the appropriate come
mend port fiber optic transmitter. As indicated in Figure
29, HI-side signals are switched in the same manner by
Quiddity multiplexer 742 in response to the CCU direction
signal from direction control circuit 740.
Referring back to Figure 27, OW selector 744 is
utilized to determine whether RUT data will be transmitted
to the CCU on the HI or LO side. Because it is only
necessary to transmit the RUT data once, one side, such as
the LO side, is preselected to carry the RUT data, if that
side is powered by power on/off control circuit 722. If
the preselected side is not powered, such as, if there is
not a POWER LATCH ENABLE LO signal to OW selector 744,
then selector 744 will allow the RUT data to be trays-
milted to CCU on the HI side. Cows addressing the RUT need
similarly be communicated across only one line. After
selecting the side from which the OW (and HOT) will be
accepted, these signals are then communicated to OW
decoder 724.
I 5
-34-
Referring now to Figure 31, therein is shown OW
decoder 724 in further block diagram form. The selected
OW and HOT signal pass to preamble and HOT stripper 750
which removes the preamble and HOT groups contained in the
OW to prevent erroneous decoding errors.
At this point, a OW and a format as follows may be
utilized for addressing a RUT.
RUT RUT RUT RUT RUT Stop
Sync Airs Opaqued Airs Opaqued Data Bit
10 000 OX XXXXX 00000 DDDDD
RUT Opaqued OX is a Nope to the Rust A 5-bit RUT
address field provides for up to 32 possible combinations.
In a presently preferred embodiment, an RUT address of all
zeros is utilized for an RUT power up sequence and an RUT
address of 31 is utilized for commands to all Ruts. This
therefore facilitates the addressing of 30 individual
Ruts.
The Opaqued and the RUT data field facilitate the
control of the RUT As will be seen from the following
chart, an Opaqued of 00 enables the assigning of a new
address to the RUT such address indicated by the 5-bits in
the data field. An Opaqued of 01 enables the last 2-bits
of the data field to be utilized to turn the C2 command
port transmitter on each of the HI and LO sides. An
Opaqued of 03 enables 4-bits of the data field to control
both command port C2 receivers and HI and LO port
receivers on an Opaqued of 05 facilitates the operation of
the RUT Of transmitter.
2 I
-35-
Opaqued Data
A B C D E
00 A A A A A
01 X X X H L
03 X H H h L
05 X X X X T
The OW, minus the preamble and HOT then passes to
Manchester II decoder 752 which changes the OW prom the
Manchester II self-clocking format to a more conventional
type of serial data format using a parallel clock. The
decoded data in serial form is then converted into
parallel form in serial-to-parallel converters 754. It
the OW contains an RUT address qualifying signal, the OW
RUT address is then compared to the Ruts assigned address
by box qualifier 756 to determine if the RUT will respond
to the OW.
Referring to Figures 32 and 33, preamble and HOT
stripper 750 is depicted in Figure 32 and Manic decoder is
depicted in Figure 33. The first transition of Man II
code causes flip-flop 758 to go I which is delayed from
transmission by ARC time constant circuit 760. After the
established time delay, preferably on the order of 2
microseconds, the preamble stripper signal on line 759
allows one shot 762 to fire. After all OW data is
received, flip-flop 758 is reset by ARC time constant
circuit 764 and the Manchester II data is clocked into
shift register 766.
The RUT OPAQUED and data field are communicated to
opaqued logic circuit 728. Opaqued logic circuit 728
preferably loads registers with data from the RUT data
buss. Opaqued logic 728 communicates the instructions
I
~36--
contained within the OPAQUED to output port enables which
selectively control transmitter and receiver operation at
the control ports in the manner described earlier herein.
OW decoder 724 also will preferably include timing
and control circuitry responsive to the OW for generating
timing signals which may be utilized to control the pro-
amble and HOT stripper 750 and boy address and qualifier
756, in addition to HI and LO-side HOT detectors (in EON
10 detector 7~36 in Figure 35).
An additional HOT detector is included within OW
decoder 724 to generate an HOT signal in the RUT when the
HOT is received from the CCU. The HOT signal from the CCU
15 is then passed to the adjacent RUT on the RUT data side.
When all RUT data on the designated return data side has
been transmitted, the RUT HOT signal is sent to RUT data
encoder 726 to start the RUT returning either its data, or
its status signal.
Referring now to Figure 34, therein is shown RUT data
encoder, (726 in Figures 26 and 27) in block diagram form.
RUT data encoder 726 serves as a data collector for
information to be transmitted to the CCU. RUT data
25 encoder 726 accepts parallel data inputs of the RUT
address, and the fault bit from the RUT power supply (720
in Figure 25~:
RUT RUT
30 no Fault RUT Indent Airs Non-Designated
1 0 F lllllllll XXXXX 15 Zeros
These data inputs are entered into parallel-to-serial
35 converters 770, such as may be formed utilizing a plus
reality of shift registers, from which the data is trays-
milted to a Man II encoder 772. The RUT data from
I
-37-
parallel-to-serial converter 770 and a preamble signal
from preamble generator 774 enter OR gate 771. During
generation of a preamble by preamble generator 774, shift
registers in parallel-to-serial converter 770 may be
keyword causing all zeros data to be presented to
Manchester II coder 778. OR gate 776 along with ENCODER
POWER SIGNAL causes EXCLUSIVE OR gate 780 to generate a
Manchester II clock pulse each -time a transition occurs in
the Man II code. As the data shirts from parallel-to-
serial converter 770, J/K flip-flop 782 toggles, coding
all the RUT data which is then transferred to LO/HI
STEERING LOGIC. To reduce power consumption, RUT data
encoder 726 is preferably powered off between RUT data
cycles by controlling the V supply to the circuit.
As will be discussed more fully later herein, an
end-of-line (EON) signal will be generated. This EON
signal denotes completion of RUT return data on the RUT
retrial data side. EON selector 727 monitors incoming data
from both the HI side and the LO side. As data comes in
from each RUT the data signal will return followed by a
gap during which an HOT signal is sent from the trays-
milting RUT to the next RUT instructing that next RUT to
transmit its data. When this gap exceeds a predetermined
limit, EON selector 727 will generate the EON signal to
instruct RUT data encoder 726 to transmit the RUT data or
status signal to the CCU.
Also included within multiplexer and master con-
troller (71~ in Figure 25) is line steering and HOT
regeneration circuitry 780, depicted in Figure 35. Cur-
quoter 780 is present for both the HI and the LO sides,
therefore only the LO side circuitry will be described
here. the restored return data from all of the Rut is
grouped together with the RUT return data by multiplexer
782. Another multiplexer 784 groups unrestored, or actual
I S
-38-
received data from both RUT LO and RUT LO receiver inputs
to form a Lucid return data signal which then passes to
symmetry restoration circuitry 717. Multiplexer 784
switches between RUT LO data and RUT LO data in response to
the EON signal generated as discussed above. When air-
quoter 786 detects an EON, multiplexer 784 switches to
transmit RUT LO data. After completion of this RUT data
transmission, an HOT signal is delayed during the trays-
mission of RUT data and is then passed on to the next RUT
to enable the transmission of data from the next line.
Line steering and HOT regeneration circuitry 780 is
further depicted in schematic form in Figure 36.
Referring again to Figure 25, therein is shown HI
side circuitry 718, including OW symmetry restoration
circuitry 719 and return data symmetry restoration
circuitry 721, and LO-side circuitry 716, including OW
symmetry restoration circuitry 715 and return data
symmetry restoration circuitry 717. HI and LO-side
symmetry restoration circuitry 719 and 715, respectively,
are essentially identical and HI and LO-side return data
symmetry restoration circuitry 721 and 717, respectively,
are essentially identical; therefore, only LO-side
restoration circuits 715 and 717 will be detailed here.
Referring now to Figure 36, therein is shown OW
restoration circuitry 715 in block diagram form. The OW
data multiplexer (742 in Figure 27 and Figure 29) inputs
LO side OW signals from OW data multiplexer 742 which
utilizes an 81.92 MHz clock in conjunction with a divide-
by-20 ring counter to yield a 4.098 MHz synchronized clock
for OW reclocking. Flip-flops in ring counter 790 are
reset at the first detected OW edge. A binary counter 794
causes the OW data to set flip-flop 792 which instructs
multiplexer 796 to switch the HOT LO signal to the appear-
private output.
I 5
-39-
Referring now to Figure 37, therein is shown LO-side
RUT return data restoration circuitry 717. LO-side return
data is input to restoration circuit 717 from OW data
multiplexer (742 in Figure 27). Retriggerable one-shot
798 forms an envelope around the OW signal. The OW passes
to restoration flip-flop 799 which is clocked by a 16.384
MHz clocking signal from divide-by-5 Johnson counter 800.
The restored LO-side data is then input into multiplexer
7~32 of line steering and HOT regeneration circuitry (780
in Figure 35).
In a seismic survey system as described herein, each
RUT 22 has a specific address by which CCU 12 will commune-
gate a OW to that RUT 22. Similarly, CCU 12 may select
lively instruct each RUT 22 to mask out any one or more data signals from the geophone arrays 28 coupled to that
RUT 22. The same address which is utilized to identify
each geophone array 26 is also used to keep track of the
placement of each seismic "shot" or energy source from we
kick energy will be recorded by geophone arrays 26. This
capability to identify shot placement and individually
access data from specific geophone arrays 26 facilitates
optimal flexibility and efficiency in three-dimensional
seismic surveying.
Referring now to Figure 39 therein is illustrated
one shooting pattern which is practical with a system as
disclosed herein. A grid is established composed of, in
this case, five lines 600, 602, 604, 606, and 608. Each
line includes 12 flags or stations, numbered 611~622.
Each "X" represents a geophone array on the lines. A
shot point may be indicated to the system through reference
to an adjacent line and station number. For example, in a
pattern as indicated, first shot location 623 may be
indicated by a three digit code indicating the line which
the shot is on or the lowest adjacent line number. In
I I
~40-
this case, the shot is on line 600 which may ye
established solely for purposes of reference of the
shot point. Therefore, utilizing a three digit line
identification code, this shot point may be indicated on
'eke X-axis located at line 600. Because the shot is on
the line, and not between lines. the next identifier of
the identification code, a between line reference, may be
0. Finally, the Y-axis of the shot location may be
indicated through reference to the next lowest station
number, utilizing a four digit station, code 0615. Each
shot on the system grid may be identified in this manner.
Where a shot occurs between lines, the fourth digit of the
eight digit number, the between line reference, may be
utilized to indicate which shot between line shot point
location the shot point represents. For example, shot point
location 624 is the only between line shot between lines
604 and 606 and is therefore "1" of "1" shot points between
those lines. Shot point 624 may thus be identified by an
eight digit code: 602-1-0615
In this manner, it is possible to keep track of all
shot points and record their location relative to the
multi-line configuration. Further, it is now possible to
accomplish both station roll and line roll operations.
This facilitates optimal flexibility in the sequence of
shot placement. For purposes of example only, if it were
desired to accumulate data for a six station split spread
relative to the shot point; i.e., a spread of three stay
lions on the grid to each side of shot point, rolling the
shot point for shot points 623-629 geophone stations 613-
618 on lines 600, 602, 604, and 606 would be utilized for
accumulation of data. As the shot point location is
advanced to the location of shot point 630, a station roll
may be accomplished by CCU 12 whereby data will be accumu-
fated from stations 614-619 on lines 602, 604, 606, and
608. This sequence can then be continued as desired.
~L23~2~
-41-
When this shooting pattern across lines 602-60~ has
been completed as desired, lines 602-608 may be powered
down by appropriate Cows from the CCU and the lines rolled;
i.e., an additional set of lines (not illustrated) powered
up such that the sequence may begin again. Because the
shot point location is identified to the CCU, the shot point
may roll along starting from left to right along one set
of lines and may then roll along stations from right to
left on the next set of lines while still maintaining a
record which is readily interpretable by data processing
equipment utilized to process the acquired data into a
three-dimensional record. Additionally, within limits of
the channel handling capacity of the CCU and the
particular convention utilized for station addresses,
because of the individually addressable Rut and Ruts it is
possible to roll from one line to another in response to
the movement of the shot point.
Referring now to Figure 40, therein is illustrated a
"Z" shooting pattern which may optionally be employed by
this system in a manner similar to that described to
accomplish a "loop" shooting pattern.
Because seismic energy expands radially from a shot-
point and dissipates as it travels away from the shot-
point, it is often desirable to vary or l'taperl' parameters
of geophone arrays such as the preamplifier gain (K gain)
on the geophone arrays in response to their distance from
the shot point. The present invention facilitates the
establishing of these parameters relative to a shot point
for each individual line within a multi-line system. Again
for example only, around shot point 637 in Figure 41 are a
variety of geophone arrays, as described with respect to
Figure 39. The Rut (not illustrated may be instructed by
to establish a first K-gain on geophone arrays located
within circle 633, i.e., stations 616 and 617 on lines 604
-42-
and 606. Similarly, a second K-gain may be established
at those stations within circle 634, i.e., stations 615-
618 on lines 602 and 608, and stations 614, 615, 618, and
619 on lines 604 and 606. Alternatively, selected go-
5 phone arrays such as those located within circle 633 may instead of being fixed with a first incremental gain, have
their received data masked within the Rut (as discussed
with regard to Figure 13) such that Jo data will be
recorded from those arrays. Again within the capacity of
lo the system as described earlier herein with regard to
Figure 39, upon instruction from the CCU, the ground
electronics of the system may advance these taper pane-
meters with the shot point.
Referring now to Figure 42, therein is shown a
seismic survey system including both "standard" geophone
arrays and alternate geophone arrays. In conventional
~ingle-line seismic survey systems, it is known to utilize
alternate geophone arrays distributed in various array
patterns to attenuate/horizontally propo~ated energy which
20 may be encountered in survey operations.
For example, a linear geophone array weighted in a
Chebychev function can reduce horizontally propagated
energy by forty dub over a wide range of frequencies. This
is discussed more fully in U.S. Patents 4,024,492 and
4,151,504 granted May 17, 1977 and April, 1979 respectively
and assigned to the assignee/applicant herein. Area arrays,
though giving more uniformed characteristics from different
azimuth arrivals, cannot duplicate-the attenuation achievable
with a Chebychev weighted function, even if the arrays include
many times the number of geophone elements.
For a linear array, the effective length of the array
is reduced as the cosine of the arrival angle. Thus, at
45 degrees the apparent length of the linear array is
.,
I
-43-
reduced to approximately 70.7 percent of the actual length
of the array and the frequency of the attenuated region is
increased as a result. The attenuation is still 40 dub in
the reject band, and thus promotes greater efficiency in
reducing horizontally propagated energy than does an creel
array. With a standard/alternate geophone array system,
having the linear arrays disposed at 90 degrees to one
another, as the arrival angle passes beyond 45 degrees,
the input may be transferred from one array to the other,
thereby causing the apparent array length to increase
again as the arrival angle approaches 90 degrees.
Therefore, with multi-line seismic survey systems,
because the shot point will typically move perpendicularly
I to some lines, it is preferable to selectively utilize
either standard or alternate geophone arrays at each
station so as to minimize these phenomenon in each portion
of acquired data. Therefore, data may be selectively
addressed from either standard or alternate geophone
arrays at each station. For example, in the example of
Figure 42, optimal data acquisition could be obtained by
utilizing alternate geophone arrays 635 in quadrants A and
C around shot point 637 and utilizing standard geophone
arrays 26 in quadrants B and C around shotpoin~ 637.
When gaps, tapers, or alternate arrays are rolled
with the shot point, the system must be programmed as to
how to advance the gaps or tapers when the shot point
advances to a position between lines or stations.
Referring now to figure 43, therein is shown a flow
chart depicting initial setup of a seismic survey system
in accordance with the present invention. The CCU is
first powered up 900. At this time the system operator
will input parameters relating to the survey operation
which he wishes to conduct 902. These parameters will
I S
-44-
then be read by the system. Once this is done, the system
will determine if a multi-line operation has been selected
904. If "yes", the system will set flags for multilane
906. The system will then accept operator input data as
to line numbers and location and as to shot line numbers
and between line shot numbers. If "no", the system will
set flags for non-multi-line, i.e., single line operation
907. If multilane operation has been selected, the system
will determine if tapered lines have also been selected
lo 908. If yes, then the system will set flags to accept
data regarding the tapered lines parameters lo. If "no",
the system will not accept tapered line data. The
determination will then be made if the operator has
decided to perform scatter shooting 912, i.e., randomly
placed shot points rather than an established pattern. If
"yes", the system is set to accept individual shot point
indexes 914. If "no", a decision is made as to whether a
loop shot advance (as depicted in Figure 39) has been
selected 916. If "yes", the system sets flags to accept
data regarding the parameters of the loop advance. If
"no", the system sets slags to accept data for a "Z"
advance as depicted in Figure 40.
As discussed previously herein, once the system is
set up and the operator elects to power up the lines, as
optical link including connector/transceivers 18 is
connected to each RUT or RUT, a portion of the internal
electronics of the RUT or RUT powers up periodically
looking for communication in the form of a OW from the
CCU. When the RUT or RUT sees the OW it fully powers up
with an address of all zeros. The unit is then
operational until communication between the CCU and that
unit stops. When this happens, the unit will then power
down after an elapsed period and go into momentary power
cycling. During power up, when the CCU needs to power the
ground units, it must power the RUT units first. The CCU
~39~5
-45-
will send a OW to the first RUT at which point that RUT
will stop cycling. When the CCU receives a status signal
from the RUT, it will then assign an address to the RUT
and instruct the RUT to turn on its transmitter so that
the OW may be communicated to the next connected RUT.
After all Russ are powered up, the CCU will preferably
power up each RUT on the first line and will then move to
the next line and power up all Rut on that line until the
entire system is powered up.
Referring now to Figures 44 A-B, therein is depicted
a flow chart indicating a system set up procedure for
multi-line operation including a tapered line operation.
As depicted in Figure l, the line at which the CCU is
located may be entered. In Figure l this would be at line
aye which is the electrical placement of the CCU.
Next, the flag designating the electrical placement
of CCU is entered 932. In a system such as that depicted
in Figure l, wherein each RUT accommodates a group 27 of
geophone arrays 26, this electrical placement will typic
gaily be physically offset to one side of Ruts 16 by four
stations.
The number of channels per line is entered 934.
Typically, one channel is assigned to each euphony array
26. The number of lines in the system is then input 936.
Where a pattern of shooting has been selected, the opera-
ion must instruct if there is a shot on line 938. If
"yes", then a flag is set for later acceptance of data
940. If "no", then step 940 is bypassed and the number of
shots between lines is entered 942. The operator then
establishes where he wants the next shot to occur 944.
This may or may not be the beginning of the pattern. If
the next shot is to occur between lines, he should India
gate which of the between line shots is to fire, i.e., if
~23~'~2~
-46-
there are two shots between lines the operator must
indicate which of these two shots is to occur next. By
entering the between line reference number 946 the open-
atop then inputs the flag of the adjacent lower station
number 948 to indicate the Y coordinate for the shot point.
The operator then enters the shot point starting and
ending roll parameters 950-956. The operator is
establishing delimiters on the shot point rolls in the
chosen pattern. The start line of the shot point is
established 950, and, if the initial shot point of the
pattern is between lines then the between line reference
number is input 952. If the shot point is to end on-line
then that coordinate is given 954, if the shot point is to
end off of a line then the between line reference number
is input 956. Parameters are then set up regarding the
geophones to be utilized at each time. A decision is
made as to whether a symmetrically split spread is desired
958. This would indicate that an equal number of geophone
arrays (26 in Figure l) to either side of the shot point
will be used to collect data. If a symmetrically split
spread is desired then a flag is set accordingly 960. If
not, selection array configuration is deferred to a later
time. The line number on which Channel l will be located
is then input 962. A selection is made as to whether
Channel No. l will be toward the high flags or toward the
low flags 964 and the system is established accordingly
966. A selection is made as to whether Channel l
direction is at low lines 968 and the system is then set
accordingly 970.
At this time the system may be set up for tapered
lines operation including gap spacing. It a gap is to be
utilized around the shot point, then the stations around
the shot point from which data is not desired are entered
972. These stations are entered in response to the next
I I
-47
shot point location which was established in steps 938-948.
The system checks to see if the split spread was
previously selected 974. If "yes", then the system goes
on to roll direction parameters. If "no", then a channel
which is desired is entered 976 and a station flag
corresponding to that channel is entered 978 to allow the
system to orient the gap.
The program then goes on to determine roll direction
parameters. If the roll direction at the end of the first
shot sequence is to high flags 980, then the step size is
input 982. If the roll direction is to low flags, then
that alternative is entered 984 prior to input of step
size 982. The system is instructed as to when to turn on
as yet unused Rut as they are approached by the roll.
This facilitates advance checking of the system. If any
takeouts, (corresponding to stations, and RUT primp
channels, are skipped, then such data is also entered
988. The number of channels per RUT is input and the
station flags establishing the upper and lower limits of
the roll procedure are input 998 and 1000. A check is
made of the initially powered Rut to see if they are
operative 1002. Appropriate signals are then indicated as
to the status of the Rut 1004,1006.
Next, tapered line parameters are entered 1007-1012.
If alternate array channels are to be selectively utilized
as depicted in Figure I then the channels for which
alternate arrays are selected are input for each line
1008. Similarly, if incremental K-gain levels are desired
on selected geophone arrays as depicted in Figure 40, then
those shameless are indicated 1010. This is repeated until
those parameters have been entered for the desired number
of lines 1012.
~23'~ 5
I
Referring now to Figure 45 BY thin is shun a flow-
chart indicating how one embodiment ox the seismic
exploration system may move the shot point record and the
data recording channels in accordance with the pro-
determined desired shooting pattern as established above As will be appreciated from the Figure, the system refers
to the shot point location and shot point roll parameters
previously entered into the system and keeps track of the
movement of the shot point and correlates the appropriate
lo channels for recording data. The shot point is recorded by
CCU 12 in response to data obtained at each shot point,
preserving an optimal data record for later processing.
In advancing the shot point and the recording
channels, CCU 12 first determines the direction in which
the shot point is to roll. An inquiry is made as to
whether the shot start line is greater than the shot end-
line 1020. If "yes", the shot point will be advanced in a
first direction 1024, toward lower numbered lines. If
"no", a flag will be set to advance the shot point in a
second, opposite, direction 1022. An inquiry is then made
as to whether the shot start line is equal to the shot end
line 1026. If "no", then the shot step is equal to the
shot step plus the direction of roll 1034. If "yes", then
another inquiry is made as to whether the shot start step
is less than the shot end step 1028. If "yes", then a
flag is set to roll the shot point in a first direction
1032. If "no", then a flag is set to roll the shot point
in a second, opposite, direction 1030. The shot step is
either incremented or decrement Ed in response to the
established direction 1034. An inquiry it then made if
the shot start step is greater than the shot between lines
1036. If "no", then the routine ends 1038. If "yes", the
shot line is either incremented or decrement Ed in response
to the established direction 1040. An inquiry is then
made as to whether the shot line has exceeded the
:~23'~
-49-
boundaries as defined by the established end line direction
1042. If "yes", then the roll is affirmed 1046. If "no",
an inquiry is made as to whether the shot is on line 1044.
If "yes", the shot step is set equal to zero and the shot
should be placed on the next line. If "no" a shot step is
flagged 1050 and the next shot should be placed between
lines. An inquiry is then made if the roll is to continue
1052. If "no", the routine ends 1054. If yes an
inquiry is made as to the advance type 1056. If a first
advance type is set, indicating a loop advance, KIWI 12
reverses the order of the start and end lines and reverses
the order of the start and end steps 1058. It a second
advance type set, for a Z-advance, then the shot line is
set equal to the start line and the shot step is set equal
to the start step 1060. it this point, the system has
accounted for rolling the shot point. The system will then
handle rolling of channel selection in reference to the
shot point. An inquiry is made as to whether the shot
points will be scattered 1062, as described earlier
herein. If "yes", then a flag is set to instruct the
operator to input the new shot point 1064. If lo then
the shot flag is set easily to the shot flag plus the step
size 1066. After this is determined, an inquiry is made
as to whether there will be tapered lines 1068. If "yes",
then an inquiry is made as to whether new gaps are desired
1070. If "yes", then the operator is prompted to input
the new shooting gaps 1072. If "not', then an inquiry is
made as to whether new channel sets are desired 1074.
These new channel sets would include parameters as
discussed earlier herein such as gaps, varied K-gains, or
standard or alternate arrays. If new channel sets are
selected, the operator is prompted to input the new
channel sets 1076. Steps 1070~1076 are bypassed if
tapered lines are not selected in the initial inquiry
1068. An inquiry is then made to whether a special shot
point is desired 1078. If "vest', the operator is prompted
~3'~5
-50-
to input a special shot point number 1080. If "no", then
the data recording channels are appropriately advanced
1082. The CCU then generates and transmits the
appropriate addresses and command words to the Rut to
appropriately program the Rut with the selected K-gain and
masking data to establish gaps; program auxiliary
channels; and program standard or alternate geophone
arrays. The system is then ready to start the recording
10~6 in coordination with the shot.
an modifications and variations may be made in the
techniques and structures described herein without depart-
in prom the scope of the present invention. Accordingly,
the embodiments described and illustrated herein are
illustrative only and are not intended as limitations on
the scope ox the present invention.
