Note: Descriptions are shown in the official language in which they were submitted.
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BACKGl~OUND OF THE INVENTION
The present invention reIates to apparatus forming
a ~ervice channel ~n a radio syst'em in which the service
channel carrier li`es at the`lower frequency end of the
radio s:ystem base ~and..
Service ch.annel' s~stems are aids in communication which
extend parallel to the'mai`n radio transmission path. They
permi`t service conver~ati.ons for maintaining operation between
radi`o stations and the.i`r reIa~ stations~ In order to make
communi`catiQns over the servi.ce.'channeI as secure as possible,
it ~5 ~no~n to exclude all operating devices from the trans-
~is.si`on and to modul~te. the service channeI signal directly onto
the emitted radio s~gnal~ Such.a proc:ess is very complicated
~nce extens.ive addi~t~onal devices are required and mainly
al~o ~e'cause this serv~ce channel is i.ntended to be used not ~.
onl~ for teIephone conver~ations but also for the transmission
o~ i`ndi.c~tion signals regarding operating states, switching
s.i`gnals to stand~-de.v~.cesr and meas-ured value signals as , ~:
~ell,
2 a 5UMM~R OF THE'INVENTI'ON
It is an object of th.e present invention to simplify
such a system and to reduce the costs required for it~
This and other objects are accomplished according to
the present invention by connecting the terminals of the -
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service channels of transmitter with receiver and data
transmission device with voice instrument each via a separate
network to a bus bar, each network including two coupled
operational amplifiers, connected so that one service channel
signal is delivered to the direct input of the first
operational amplifier, the first amplifier output is connected
1. to the bus bar via a resistor;
2. to the negating input of the second
operational amplifier via a first voltage divider; and
3. in feedback to its own negating input
via a second voltage divider; and the direct input of the
the second operational amplifier is connected, via a further
resis-tor, with the bus bar. In the network associated with
the transmitter with receiver, the direct input of the first
amplifier receives the service channel signal appearing in the
receiver and the output of the second amplifier is connected
to the transmitter.
To complete the system the data transmission device with
voice instrument has a similar network whose first amplifier
has its direct input connected to receive signals Erom the
data transmission device and the transmitter part of the
voice instrument, and whose second amplifier has its output
connected to the input of the data transmission device and the
receiving part of the voice instrument, each via a further
resistor, filters being connected ahead of the receiver and
the transmitter of the voice instrument. The invention can
be modified by connection of further transmitters with receivers
connected to the bus bar.
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Due ~o the grou~ed connection of the service line
channels to a bus bar, this service line system is very much
simplified and is expandable in any respect. The use of
operational amplifiers completely prevents transmission of-
an incoming conversation to the associated transmitter.
This is accomplished by a feedback connection of the incoming
conversation at the negating input of the operational
amplifier which is connected ahead of the transmitter.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a diagram of an embodiment of a circuit
arrangement according to the invention for a transmitter with
receiver.
Figure 2 is a diagram similar to that of Figure 1 showing
two networks connected together via a bus line for a receiver
with transmitter and data transmission device with voice
instrument.
Figure 3 is a block diagram of a circuit for a combination
utilizlng a simple end position.
Figure 4 is a diagram similar to that of Figure 3 of
a combination at a relay station with substitute instruments.
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DES:CRIPTI:ON OF THE RRE:FER~ED EM~ODIMENTS
In the circuit shown in Figure 1, the incoming service
channel from a receiver Eml is connected to the~direct input
terminal of a first operational amplifier Vl. An input
resistor Rl is connected between that input and ground.
The output of the operational amplifier Vl is connected via
a resistor R4 to a BVS line. The output of amplifier Vl
is also connected via a first voltage divider R5/R7 to the
negating input of the second operational amplifier V2, and
via a second voltage~divider R2/R3 to its own negating input.
The input to a transmitter Sdl is connected to the
output of a second operational amplifier V2. The di.rect
input of amplifier V2 is connected to the BUS line via a
resistor R8. The BUS line is terminat:ed by a resistor R9.
The value of resistor R9 is dependent on the number of identical
networks, n, connected to the BUS line and is calculated as
follows: R9 ~ . The input resistance of amplifier V2 can
: be neglected because it is much greater than R9.
A conversation signal coming from receiver Eml reaches
transmitter Sdl via the ~irst operational amplifier Vl, a
:resistor R5 and the se~ond operational amplifier V2. This
signal is delivered to the negating input of amplifier V2 to
which feedback resistor R6 is connected. The voltage divider
R5/R7 couples this signal from receiver Eml to the negating
input of the second operational amplifier V2.
The signal from the.output of amplifier Vl is also
conducted via resistor R4, the BUS line and resistor R8
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to the direct input of ampli~ier V2 and the signals fromampli`fier Vl reaching the inputs of amplifier V2 cancel
one another out and become zero so that the transmit~er Sdl
is not provided with any signal component from the signal
from receiver Eml.
The voltage divider R2/R3 between the output and the
negating input of the first operational amplifier Vl and the
resistor R6 between the output and the negating input of
the second operational amplifier V2 constitute feedback
connections which serve to regulate the total gain of the
individual amplifiers and to stabilize the degree of amplifi-
cation.
Figure 2 shows a circuit arrangement providing the elements
for the service channel for a receiver/transmitter at the same
location as the arrangement and for a data transmission device
with voice instrument remote from the arrangement and connected
together via a sUS line. The arrangement is a receiver module in
which the signal arriving at receiver Em is ~ed to the direct
input of operational amplifier Vl via terminals a and b of
a plug-in strip. Amplifiers Vl and V2 correspond to those
of Figure 1, but the details of the circuit elements shown in
Figure 1 are not shown here but are present in an actual
circuit. The operational amplifier V2 has its output connected
to terminal d and is connected with the transmitter Sd. The
BUS line for the entire system is connected to terminal c. ~ -
The BUS line is further connected to coupled further
operational amplifiers V3 and V4 associated with the remote
a~
transmission device with voice instrument. The incoming line DT. from
ln
the data transmission device is connected via terminal e to the direct
input of the operational amplifier V3, to which is alsu connected the
transmitter part SP of the voice instrument, both lines being decoupled
via a resistor.
The output of the fourth operational amplifier V4 leads to the
data transmission device output line DT t' at terminal f~ and to the
receiving part RP of the voice instrument. Both of those lines are likewise
decoupled via resistors.
Connections to parts SP and RP are effectuated via low-pass
filters F. The filters F limit the speech band at 2,4 s in order that
above this frequency the band is free for transmissions of control signals.
The feedback connections of Figure 1, which are not shown in
detail in Figure 2 are also provided for the circuit unit of amplifiers V3
and V4 and prevent the incoming conversations from receiver Em from
returning into the associated transmitter Sd. This applies as well for the
transmitter and receiver parts of the voice instrument and for the data
transmission device at terminals DT.
Figure 3 shows an em~odiment of a circuit provided for a simple
end position~ A simple end position is connected to the end of a spark
gap, and this simple end position receives from one direction respectively
transmits to one direction otherwise to relay station (Fig. 4), which
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receives from many directions respectively transmits to many directions.
The circuit in the brokenline box corresponds in its details to
the circ~it arrangement of Figure 2. The circuit Eml contains the receiver
connected at terminal b and the circuit Sdl contains a transmitter Sdl
connected to its service line at terminal d.
Figure 4 shows a circuit combination of instruments in a relay
station. Here the active instruments are shown schematically in the
drawing as Eml, Em2, Sdl and Sd2. Receiver Eml and transmitter Sdl which
correspond to those of Figure 2, receive and send in the opposite directions
from receiver Em2 and transmitter Sd2. Also are shown standby instruments,
i.e. a receiver Eml~, transmitter Sdl', receiver Em2' and transmitter Sd2'.
The switches Sl and S2 inserted in the interconnection are
electronically controllable switches which switch the system to the standby
instruments when there is a malfunction in the active devices.
The relay station in Fig. ~ enables to receive a signal from two
directions "All and 'IBII and to transmit a signal to two directions "A" and
'BII .
The notation of the terminals for connection are the same as in
Fig. 2.
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It will be understood that the above descr.iption of
the present invention is susceptible to various modifications,
changes and adaptations, and the same are intended to be
comprehended within the meaning and range of equivalents
of the appended claims.
