Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
~9F~668
TELEl\IETRY ACCESS ARRANGEMENT
This is a division of co-pending Canadian Patent Application Serial No.
2,043,598 which was filed on May 30, 1991.
Technical Field
This invention relates to a method and apparatus for accrssing customer
5 meters and for controlling customer devices over a telecommunications line.
Problem
There has long been a need for reading utility meters periodically, a need
which in the past has been met largely through manual arrangements. More recently,
there has also been a growing desire by the electric power utilities to be able to control
10 consumer electric loads as a means of forest~lling brownout and blackout situations. This
need has been met with only partial success in the prior art by telemetering arrangements
associated with telephone customer line access and by the use of carrier systemsconnected to power distribution lines. In these arrangements, utility meters at a
telephone customer's home or business are accessed via the telephone customer's line
15 when that line is not being used for telephone calls. The method of accessing the line is
to have a direct metallic path between the customer's meter reading interface and a
service unit at the central office for monitoring and controlling the off-hook/on-hook
supervisory state of the customer. Access from the central office switch to the customer
is provided through the use of a no-test trunk, i.e., a trunk which can access a customer's
20 line even when that line is already in the off-hook state. The trunk uses a no-test
connection, i.e., a special metallic connection that bypasses the normal switched telephone
connection and connects without making a busy test. This metallic connection passes
direct current signal. The no-test trunk is used to get access to the meters without ringing
the customer's line, the latter action being performed on all conventional telephone
25 connections. The meter is then triggered to respond by being sent signals over the no-test
connection, each signal consisting of a burst of tone of one of thirteen frequencies in the
telephone voice band. Using this arrangement, a connection is established to thecustomer's line, the service unit makes a test whether the customer is busy, and, if the
customer is not busy, the service unit is connected to the customer's meter interface. The
30 meter interface is primed (alerted) by one of the thirteen frequencies to respond to data
2 2095668
signals originating from the service unit or a controller at the utility, transmitted via the
service unit. These data signals may be either in the form of dual tone multifrequency
(DTMF) signals or frequency shift keyed binary data signals. Following the alerting of the
meter interface unit, there is an exchange of ~ign~ling information between the controller
5 and the meter interface unit, the sign~ling exchange being used for triggering the reading
of meters, for transmitting the present reading of the meters, for returning the present
status of these meters, or for controlling a device such as an air conditioner at the called
customer's residential or business location. The latter function allows a power company to
control its peak load by temporarily shutting down, possibly on a rotating basis, a portion
10 of the air conditioners being served. The actual reading of the meters is performed by a
reading mechanism that interfaces with the meter interface used Meter status information
includes indications of customer tampering, low battery, or other indications of a need for
servicing. After a complete cycle of meter readings and/or device control operations has
been completed, the no-test connection is dropped and the customer is enabled to15 originate new calls.
While the customer's line is connected to the service unit, supervision of
the customer's line is perrormed by the central office service unit (C.O. service unit)
which is connected by a metallic access connection that provides current sensingsupervision from a central office service unit. In modern digital switching systems, such as
20 the 5ESS~ switch manufactured by AT&T, and described in The AT&T Technical
Journal, July/August 1985, no metallic access connection is provided through the voice
network, so that a no-test trunk is required for monitoring direct current supervisory
signals. If the customer's telephone station goes off-hook, a direct current in excess of 20
milli~mperes is detected by the C.O. service unit and the central office service unit
25 disconnects the telemetry call. In some cases, the supervision is performed from the
customer's meter interface unit which transmits a disconnect signal to the central office
service unit to disconnect the telemetry call.
There are a number of disadvantages to this arrangement. The no-test
trunk is a facility available in very small numbers in a central office, the number being
30 limited by the no-test access arrangements. No-test trunks are used primarily for checking
on customers whose lines are reported as being busy for too long a time, making tests of
the resistance between the two wires of a customer line, and manual testing of a line. In
`~ 3 2095668
a typical switch, such as the SESS switch, only two no-test trunks are available in an entire
switch, which may serve up to several hundred thousand customer lines. In a typical
meter reading cycle the time required for meter readings and/or device control operations
may vary from 10 to 20 seconds. Clearly, two no-test trunks are inadequate to serve the
meter reading and device control needs of all the customers of the SESS switch. Further,
the requirement for a direct metallic path in order to provide current sensing supervision
makes it difficult to access lines which are not connected directly to a switch but are
connected through a subscriber line carrier system, such as the SLC 96 (Subscriber Line
Carrier) manufactured by AT&T, since such SLC systems do not provide a metallic path
for a normal voice connection. Further, billing records for such no-test trunk calls are
made separately from the billing records for voice or data calls, thus creating
administrative problems. Further, in prior art arrangements, if a customer wishes to
originate a call while the meter reading is taking place, there are some arrangements in
which the customer is blocked until the reading is completed and other arrangements in
which the customer is blocked for a period of 1 to 2 seconds until the no-test connection
can be dropped.
Because of the small number of no-test trunks and limited no-test access,
and the fact that the no-test trunks are needed for their primary intended purposes, the
number of meters which may be monitored and devices which may be controlled is much
smaller than the number of such meters and devices served by a typical large local central
office. It is costly to add substantial numbers of extra notest trunks, in a digital switch
such as the 5ESS switch which does not provide a metallic access voice switching network,
because the metallic access unit provided for such no-test trunks is expensive. A problem
of the prior art, therefore, is that there is no arrangement available which permits a large
central office, especially a digital central office which does not provide a direct metallic
path for telephone connections, to access a large number of meter reading and device
control interfaces within a reasonable period over the customer lines connecting that
central office to the telephone stations and the remote metering devices.
Solution
The above problem is solved, in a departure from the prior art by providing,
for example, arrangements wherein a standard interoffice trunk, controllable by special
software of the connected switching system, is used for accessing, over an analog customer
2095668
line, a customer's premiscs device such as a meter interface unit (MIU) from a data
access device, such as a utility meter reader/device controller; this standard trunk is then
connectable to the customer's line via a suppressed ringing connection through the
communication signal switching network, used, for example, for voice signals, in order to
5 access the customer's analog line, connected to the MIU. Advantageously, such an
arrangement makes it possible to use a plurality of circuits for accessing different meter
interface units at the same time and without requiring additional expensive specialized
no-test trunks.
Modern digital switching systems, such as the SESS switch, do not provide a
10 metallic connection that can pass direct current signals; metallic access facilities are
expensive in digital switches because they bypass the digital network which is used for
passing speech signals for telephone conversations. The switching network need not
provide a metallic access from the C.O. service unit to the line because supervision is
detected at the line circuit, an interface between the switching network and the customer
15 line, and is passed by the software controlled processors of the switch to the connected
trunk, which passes supervision to the C.O. service unit. Trunks such as the well-known
E & M trunks or trunks using common channel sign~ling have arrangements for
communicating a change in supervisory state at one end to the other end of the trunk.
These arrangements are used to transmit customer supervisory state changes to the C.O.
20 service unit so that the unit may disconnect if a customer goes off-hook.
In the prior art, the only way of getting access to a customer's line using
the standard switching network or switch fabric was to ring the customer's line, and to
monitor supervision from a line circuit in the switch. In a departure from the prior art, a
new type of call connection is made in which ringing is suppressed in order to avoid
25 alerting the customer; supervision is monitored by the switch and transmitted via the
software controlled processors and trunk supervisory signal transport techniques to a
monitoring central office unit. The meter interface unit is alerted without ringing the
customer's line from a connection through the standard switch fabric of the central office
by providing a new class of service for calls from the utility, the new class of service being
30 characterized by a connection made without such ringing. In this case, the class of service
is a class of service of the caller and affects the nature of the call being set up. The
2095668
meter interface unit is alerted that a connection to the meter interface is desired by a
tone sent to the interface unit by the C.O. service unit, or, alternatively, by the utility
controller through the service unit. The interface unit receives these tones while in the
on-hook state and processes them without sending an off-hook signal back to the central
5 office.
Billing records are made in the normal way that billing records are made
for calls through the switching network. Advantageously, this type of call connection can
use the normal switch fahric for accessing a customer line, while also providing the
absence of ringing necessary to access the meter interface unit without disturbing the
10 customer, and while continuing to use normal customer supervision from the switch.
Present-day subscriber line carriers (SLCs) will not set up a connection
unless they detect ringing. An exception to this rule is for a connection from a notest
trunk wherein a special tone is provided which is recognized by the subscriber line carrier
and which will then provide a metallic bypass of the SLC. In accordance with one aspect
15 of the invention, when a meter interface unit access call is set up through a subscriber line
carrier, a brief burst of ringing is applied on that connection. In response to that brief
burst of ringing, the subscriber line carrier sets up a connection within its own switch
fabric to the called customer whose meter interface unit is being accessed. The burst of
ringing is sufficiently short that the subscriber line carrier which repeats any ringing signals
20 that it detects on its input, will not in fact repeat any ringing signal to that customer's line,
thus, avoiding disturbing the customer when only the meter interface unit is being
accessed.
A central oflice service unit interfaces between a utility controller, such as apersonal computer, at the utility and the meter interface unit connected through the voice
25 signal switching network. Responsive to signals from the utility controller, the central
office service unit signals the switch with the identification of the called customer to set
up a suppressed ringing connection to the desired meter inter&ce unit. The central office
service unit or utility controller transmits alerting signals to the meter interface unit. The
central office service unit detects off-hook signals from the switch in order to signal for a
30 premature disconnect, and responds to a meter interface unit disconnect signal to signal
the switch for a disconnect of the meter reading and/or device control connection. The
2095668
central office service uniL has a plurality of interoffice trunks for communicating with
customers connected to other switching systems and for communicating simultaneously for
reading several meters in parallel for customers in these switching systems; it also is
connectable to a plurality of utilities for simultaneous use over different trunks.
S In accordance with one aspect of the invention, for an Integrated Services
Digital Network (ISDN) station connected via a Primary Rate Interface or a Basic Rate
Interface, and a digital line, the D-channel is used for communicating with the meters and
controllable devices. This also permits the communication signal switching network to be
used for providing access to the customer's lines and allows the high bandwidth (6t or 16
kb./sec.) D-channel to be utilized for communications with the meters and devices. Here,
supervision is detected at the customer premises and is transmitted by data signals over
the D-channel.
Accordingly, this invention provides a method and apparatus for accessing
customer premises devices from a data access device by using a suppressed ringing
connection through a voice signal switching network of a telecommunications switching
system.
In accordance with one aspect of the invention there is provided a method
of accessing a customer premises device from a data accessing device via a
telecommunications swiLching system, said telecommunications switching system comprising
a voice band signal switching network for switchably interconnecting multiplicities of inlets
and multiplicities of outlets, said inlets for connection to interoffice telecommunications
trunks, said outlets for connection to analog customer lines, the method comprising:
determining that a class of service for an inlet connected to said data accessing device is a
class of service requiring establishment of a suppressed ringing connection; establishing a
suppressed ringing connection from said inlet to an outlet of said voice band signal
switching network for connecting said data accessing device to an analog customer line
connected to station equipment of a customer; and transmitting signals over saidsuppressed ringing connection for accessing said customer premises device over said
analog line from said data accessing device; wherein said establishing comprisesdetermining whether said station equipment is connected via a subscriber loop carrier,
and, if so, sending a brief spurt of ringing signal over said connection for enabling said
subscriber loop carrier to establish a connection to said station equipment without
transmitting a substantial ringing signal to said station equipment.
20q5668
In accordance with another aspect of the invention there is provided a
telephone switching system comprising: a switching network for interconnecting amultiplicity of telecommunications trunks and another multiplicity of analog customer
lines; at least one of said trunks connectable to a utility data accessing device for
S acce~cing a customer premises device; processor means operative under the control of a
program for translating a class of service of said at least one of said trunks, and
responsive to said translating, for establishing a connection through said network without
transmitting ringing signals to an analog customer line; and wherein one of said customer
lines is connected to customer premises equipment through a subscriber loop carrier and
wherein said processor means is further operative under the control of a program for
sending a brief spurt of ringing signal over said connection to said one customer line for
enabling said subscriber loop carrier to establish a connection to said one customer
equipment.
Brief Description of the Drawin
The present invention, taken in conjunction with the invention contained in
co-pending Canadian PaLent Application Serial No. 2,043,598 will be described in detail
hereinbelow with the aid of the accompanying drawings, in which:
FIG. 1 is a block diagram illustrating connections for accessing customer
meters and devices; and
FIGs. 2-6 are flowcharts of actions performed in setting up such
connections and in accessing meters and devices.
Detailed Description
FIG. 1 is a block diagram of the operation of applicant's invention. A
terminal such as a personal computer 10 at the office of a utility is connected by a line or
connected over an interofrice trunk to a telephone switch 21. When an access number is
dialed and received from PC 10 in switch 21, a connection is set up to a central office
service unit 20. The central service unit is located herein in a first central office that
includes switching system (switch) 21. In alternative arrangements, the central office
service unit disconnects PC 10 and dials back to access PC 10 in order to guard against
tampering of the meter reading and device control process from unauthorized sources.
This central office (C.O.) service unit 20 is connected to a plurality of central office
switches, such as switch 21 and 22 by utility telemetering trunks which are simple
interoffice trunks. Each of the switches 21 and 22, which may be housed in different wire
8 2095668
centers, has a switching network, 23 and 24, respectively, for transmitting communications
signals, such as voice signals, and including the meter reading and device control signals of
this invention. Each o~ the switches comprises control processor means 26, operative
under the control of a program 28, stored in memory 27 for controlling the operations of
5 the switch. In response to signals received from PC 10, C.O. service unit 20 requests
utility connections by sending signals similar to the kinds of signals sent for setting up an
interoffice call to the appropriate one of switches 21 or 22.
In this specific embodiment, the method used for signaling the request to be
connected via a customer line to a particular metering interface unit (MIU) such as MIU
30, MIU 32 or MIU 35 is to send out a string of multifrequency (MF) digits. Such a
string of digits usually consists of a key pulse signal (KP), a four, five, seven or ten digit
directory number and a start (ST) signal. In response to reception of these digits, a switch
such as switch 21 translates the received directory number to identify a meter interface
unit such as meter inter~ace unit 30 and sets up a connection via a utility telemetry trunk
(UTT), between the central office service unit 20, through a switching network 23 or 24,
via a customer line to a MIU 30, 32 or 35.
The utility telemetry trunk has a special class of service which identifies to
the connected switch that the requested connection is to be made with ringing suppressed.
In response to a received directory number from a UTT, switch 21 sets up a connection
20 with ringing suppressed to MIU 30. Note that a suppressed ringing connection differs
from a conventional voice connection, not only in that a ringing signal is not sent and that
the line is not monitored ror a supervisory signal to stop or "trip" ringing, but that no
check is made that a ringing signal is actually flowing to the analog line. The ringing
signal and its accompanying checks are a basic and inherent part of any normal telephone
25 connection. For example, even when a facsimile call is completed, wherein no audible bell
is heard, the circuits of the terminating facsimile machine respond to the ringing signal
that is sent from the switch.
When the suppressed ringing connection to the MIU has been established,
MIU 30 is connected to C.O. service unit 20 and receives from that service unit or from
30 PC 10 through the service unit an alert tone to trigger the MIU into the telemetry mode.
In accordance with the principles of this invention, wherein a customer's station
equipment includes both a voice or other communication station and an MIU, the normal
ringing signal alerts the communication station, and, where this is a voice station, thereby
2095668
~ g
alerts the customer, while the tone signal sent over the suppressed ringing eonnection
alerts the MIU. Telemetry and control signals are then exchanged between C.O. service
unit 20 or utility controller 10 and MIU 30 and the data received from MIU 30 istransmitted from C.O. service unit 20 to PC 10 for processing by the utility. Similarly,
5 utility eontrol signals are sent from PC 10 to C.O. service unit 20 for transmission to MIU
30 to eontrol deviees at the customer's home. If a eustomer pieks up the handset of a
telephone station while ~he communieation between the serviee unit and the meters
and/or deviees at the customer's location is in progress, these communications are quickly
terminated and regular service restored to the customer. An incoming eall, however, will
10 reeeive a busy signal if a utility access eall is in progress.
The UTT is a conventional interoffiee trunk sueh as an E & M trunk or a
eommon channel signaling trunk. Such trunks have arrangements whereby a change of
supervision a tone end is signaled to the other end by a tone (E & M) or by an out of
band tone or data signal. Such a trunk passes a supervisory signal, detected at a line
15 circuit and passed by the switch processor to one end of the trunk, to the C.O. serviee
unit to effeet a disconnect of that unit when a eustomer goes off-hook in the middle of a
utility aeeess eall.
The C.O. service unit is expanded from prior art C.O. service units to be
eonnected by trunks to a plurality of switches, such as switeh 21,... ,22, and is eonnectable
20 by a plurality of trunks (a trunk group) to each sueh switch. In some cases, several trunk
groups may be connected to one switch, for example, to handle traffie to different groups
of SLCs. The C.O. service unit is also connected to a plurality of utilities, only one of
which is shown, which simultaneously establish ealls to different customers.
While in this embodiment, the utility aeeess unit PC 10 is eonneeted to the
25 MIU through a service unit, an alternate eonfiguration would permit a utility access unit
to be eonneeted via a trunk directly to the switching network for connection to the MIU.
The specific embodiment of FIG. 1 uses an analog line, transmitting voice
band signals, ringing or tone alerting signals, and using direet eurrent deteetion of
supervision. The term "ringing" as used herein is used for eonvenience and because of its
30 common use, but is meant to describe any proeess of customer alerting, including, for
example customer tone alerting. For Integrated Services Digital Network (ISDN) lines,
supervision and customer alerting signals are transmitted as data signals over the D-
channel of the customer line.
2095668
-- 10
FIG. 1 shows details of a meter interface unit. A protection circuit 40 is
used to protect the rest of the meter interface unit 30 against damage caused by electrical
signals carrying excessively high energy. Effectively, this is over-voltage protection. Such
protection circuits are well known in the prior art. Alert circuit 42 is used to detect the
S initial alerting tones used for sign~ling a request for a connection to the meter interface
communication circuit 46. The alert circuit continuously monitors the line when the line is
on-hook in order to detect such signals. When such signals are detected, it activates the
meter interface communication circuit which communicates with PC 10 to exchange the
reading information from meters and the control information on meters 50 and thecontrol information for controlling devices 48. When a control and/or reading cycle has
been completed as determined by the C.O. service unit 20, the C.O. service unit goes
on-hook which triggers switch 21 to send a 300 millisecond minimum open loop signal to
the MIU to signal a disconnect.
In some cases, certain SLCs such as AT&T's SLC 96 will not transmit a
forward disconnect (open). In many cases it will. It depends on the channel units
installed. If the disconnect is not forwarded, then the MIU detects the end of data
transmission and notifies the C.O. service unit during the data transmission, and the C.O.
service unit detects the end of data transmission and disconnects to connecting trunk.
Depending on the channel unit inventory situation, the telephone service supplier may
wish to allow off-hook transmission. In this case, the MIU detects the end user off-hook
signal in order to signal ror a disconnect of the suppressed ringing connection. In any
case, it is to provide the forward disconnect through the appropriate channel units.
As long as the meter interface unit 30 presents an impedance in excess of
app~ "~t~ly 10k ohms to the line, the central office will treat the line as being on-hook.
If the customer should pick up his telephone instrument while the communication between
the PC and the meter interrace unit is going on, switch 21 will detect the off-hook and
cause the communication between the PC and the meter interface unit to be aborted by
sending a disconnect signal to the MIU and an on-hook signal to the C.O. service unit to
terminate the connection.
Arrangemcnts for communicating with on-hook devices such as the meter
interface unit 30 are well known in the prior art and are defined, for example, in Bellcore
Technical Reference TR-TSY-00003()~ Issue 1, June, 1988.
209566~
- 11
FIGs. 2-6 ~lre flow charts showing the call processing actions that take place
while processing a utility telemetry call. FIG. 2 shows the frst steps in response to a
seizure from a utility telcmetry trunk. As shown in FIG. 1, utility telemetry trunks, which
are ordinary interoffice trunks, are connectable to different switches. The trunk is
originally in the idle state. It goes off-hook (action block 203) and a wink start signal is
received from the trunk (action block 205). This is followed by the digit reception state
(action block 207). FIG. 3 is a flow chart in response to digit reception. If the trunk goes
on-hook during or following digit reception (action block 311), the call is considered
abandoned (action block 313) and the trunk is taken down (action block 315) and
restored to the idle state (action block 317). If there is a timeout or no digits are
received as determined by the tests in the interdigit timing (test 321), then the call is
considered abandoned (action block 341), the trunk is taken down (action block 343) and
is restored to the idle state (action block 317). If the digits are properly received, the
digits are analyzed (action block 323). If the ST signal is the standard ST signal (ST0) as
determined in test 325, the routing sequence 329 is entered. Otherwise, the type of
alternate ST signal (ST1, ST2, or ST3) is used to determine the length of a requested
burst of ringing and this burst of ringing is requested for application after a connection
has been set up to the requested meter interface unit. In this specific example, the length
of the bursts are 20, 40 and 60 ms.; further experimentation may indicate that other
lengths, such as 50, 100 and 150 ms. may be preferable to take into account, for example,
variations in the ability to control the length of a burst. The best arrangement is to
permit the length of the hurst to be a parameter controllable by the translation recent
change facility of modern switches. If more than 3 different lengths (plus 0 length) are
required, different groups ot utility trunks are used for different groups of ringing burst
lengths; for example, group A could be used for 0, 20, 40 or 60 ms. bursts, while group B
could be used for 0, 80, 100 and 120 ms. bursts. The burst of ringing is used in the SLC
to assign a time slot for the connection to the customer's MIU, but is sufficiently short
that it is completed before the connection is actually made; thus, no ringing signal is sent
to the MIU. Thereafter, ~he routing sequence 329 is performed. FIG. 4 is a flow
diagram of the steps of the routing sequence. First, a determination is made by test 401
whether the call is an inlerswitch call. If so, this indicates an error 403 since the utility
telemetry trunk used on the call is supposed to be connected to the switch serving the
requested meter inter~lce unit. If this is not an interswitch call, then test 405 determines
- 209566~
12
whether the called cus~omer associated with the requested meter interface unit is busy or
out of service. If so, then the busy or out of service status is returned to the trunk
control program and further actions are performed as described in FIG. 5. If the called
customer line is not busy or out of service, then the connection is cut through if necessary
with the abbreviated ring as derived in block 327 (action block 409). When the call is cut
through to the end user, a trunk off-hook signal is returned to the C.O. service unit 20.
The trunk then goes into the telemetry data wait state (413). FIG. S describes the actions
performed if the called customer associated with the requested meter interface unit is
busy or out of service (state 407). An on-hook signal is sent over the utility telemetering
trunk to the C.O. service unit 20 (action block 501) and the trunk is taken down (action
block 503). The trunk is then in the idle state (317).
In the telemetry data wait state, it is the responsibility of the C.O. service
unit, responsive to signals from the utility controller or internally triggered, to alert the
MIU. Using today's equipment, the MIU is alerted by one of 13 single frequencies. Once
the MIU has been alerted, other signals such as frequency shift keyed data signals can be
used for communicating with lhe MIU. The end user cannot alert the MIU because the
user's station equipment does not have a one-of-13 single frequency generator and,
further, the call would be taken down if the end user went off-hook.
FIG. 6 is a Llow diagram of the actions performed in response to various
timeout conditions and in response to disconnect signals. The switch is in a wait state
(413) during the telemetry connection. If a maximum interval such as 10 or 20 seconds is
exceeded (action block 611), the customer's line is disconnected and a signal is sent to the
MIU to disconnect (action block 613), an on-hook signal is sent over the utilitytelemetering trunk to the C.O. service unit (action block 615) and that trunk is taken
down (action block 617) and restored to the idle state (317). The same disconnect
functions are performed upon completion of a telemetry access call. A billing record is
then made in the same way as a billing record is made for a conventional (voice) call. If
an on-hook signal is detected on the utility telemetering trunk, indicating a disconnect
from the utility side (acLion block 621), then the line connected to the metering interface
unit is disconnected (action block 623), the utility telemetering trunk is sent an on-hook
signal (action block 625), the trunk is taken down (action block 627), and restored to idle
(317). If an overload or other condition is detected in the switch, indicating that
telemetering activities should be temporarily suspended (action block 631), then the
2095668
_ 13
customer's line is disconnected (action block 633), an on-hook signal is sent over the
utility telemetering trunk (action block 635), that trunk is taken down (action block 637)
and restored to the idle sLate (317). If the end user goes off-hook during the telemetering
interval because the end user wishes to place a call (action block 641), then the line is to
5 be disconnected from the telemetering connection, a disconnect is sent from the switch to
the MIU (action block 643), the utility telemetering trunk is sent an on-hook (action
block 645) and the trunk is taken down (action block 647). The end user is then prepared
to be processed in the normal way by receiving dial tone and placing this call by dialing
the app~opliate digits (state 649).
It is to be understood that the above description is only of one preferred
embodiment of the invention. Numerous other arrangements may be devised by one
skilled in the art without departing from the scope of the invention. The invention is thus
limited only as defined in the accompanying claims.
