Radio Digital Processor 1A12A16, Asynchronous Mode

TM 11-5820-695-35

converts it to half baud for cable system compatibility.

The pcm signal is then combined with the orderwire

digital processor 1A12A10 generates signals ONOR and

signal and applied to the cable system.

1RPFAIL. When signal 1RPCM is normal, if the CABLE

(1) When the CABLE LOOP TEST switch

LOOP TEST switch is in NORMAL position, signal

(1A12A12AlS1) is in the NORMAL position, signals

1RPCM is gated through A7B and following circuits into

OTEST and OCLPCM are both logic one. Signals

the secondary of T1. Signal ONOR output from the

1RPCM (waveform A, fig. 638) and 1R2304 (waveform

traffic detector is then logic one, signal 1RPFAIL is logic

B) are combined by NAND gate A7B. The full baud

zero, and the radio-to-cable pcm signal is transmitted

1RPCM signal is converted to half baud at the output of

through the cable. If the CABLE LOOP TEST switch is

A7B (waveform C, fig. 5-38). This signal is inverted by

then placed in TEST position, signal 1RPCM is inhibited

OR gate A4D (waveform D) and applied to pulse

at A7B (logic zero at pin 6) but signal OCLPCM is gated

generator A2, which is a monostable multivibrator.

through A4D. Signals ONOR and 1RPFAIL are the

When the output of A4D goes negative (low), the output

same as above but now the cable loopback pcm signal

of A2 goes negative for 217 nanoseconds (1/2-baud),

is sent to the cable. When the radio-to-cable pcm signal

then returns to high (waveform E, fig. 5-38). The output

(LRPCM) fails, if the CABLE LOOP TEST switch is in

signal from A2 is inverted by A4C and applied to the

NORMAL position, there is no pcm signal into T1.

cable output amplifier (waveform F, fig. 5-38).

Signal ONOR switches to logic zero and signal 1RPFAIL

switches to logic one (traffic failure). There is no pcm

(2) In the cable-to-radio direction of

signal in the cable. If the CABLE LOOP TEST switch is

transmission, the pcm signal is sent to the modulator

then placed in TEST position, signal OCLPCM is gated

circuits of Transmitter, Radio T-1054/GRC-144 for

through A4D.

Signal ONOR is logic one, signal

transmission after being processed in digital data

1RPFAIL is logic zero and the cable loopback pcm

modem 1A12. This signal, inverted (OCLPCM from

signal is sent to the cable. The logic state of signal

cable digital processor 1A12A4), is applied to radio

ONφR affects operation of relay 1A12A-12A2TB1K1.

digital processor lA12A10. When the CABLE LOOP

See e below.

TEST switch lA12Al5A1Sl is placed in the TEST

position, this from cable signal is substituted for the from

(4) Switch Logic. The switch logic circuits are

radio pcm signal through OR gate A4D. Thus, under the

for future application and are not used.

test condition, the signal from the cable is returned

c.1 .

Radio Digital Processor 1A12A16,

directly to the cable as a means of testing the cable

Asynchronous Mode. (fig. 5-8.1 and 5-38.1). Radio

system.

digital processor 1A12A16 receives the full baud,

(3) The pcm signal from A4C is amplified by

retimed pcm signal (LRPCM) from 1A12A9 and converts

cable output amplifier Q1 and transformer coupled to

it to half baud for cable system compatibility. The pcm

the cable circuit and the traffic detector.

signal is then combined with the orderwire signal and

applied to the cable system.

(a) There are three cable simulation

networks; each network provides attenuation equivalent

(1) The function logic switch determines the

to 1/4-mile of cable. They are added in the required

output signal provided by 1A12A16. When the CABLE

increments to make the total length of actual and

LOOP TEST switch (1A12A12A1S1) is in the NORMAL

simulated cable equal one mile.

A selector plug

position, signal OTEST is logic 1 and signal OCLPCM is

connects the required networks and also makes a

inactive and the input is a constant logic 1. When the

connection to the applicable CABLE LG (MILES)

CABLE LOOP TEST is in the TEST position, signal

indicators on the front panel. A similar arrangement is

OTEST is logic zero and signal OCLPCM is active.

provided for cable digital regenerator 1A12A2 (para 2-

(a) When signals OTEST, TC1 and

5a) such that when both special connectors are plugged

TC2 are all logic, the output of inverter A6D is logic 0.

in to simulate the same length of cable, the associated

The outputs of NAND gates A6C and A4B are then fixed

CABLE LG (MILES) indicator is lighted (para 2-39d).

at logic 1, and NAND gate A5A has logic 1 at two inputs

(b) At

the

secondary

side

(pins 1 and 2). NAND gate ASB has logic 1 at pin 8

transformer T1, the pcm signal is combined with the

(OTEST) and the 1RPCM signal is gated through A5B

orderwire signal and the cable direct current. The

by the

overvoltage shunt circuit protects circuits of radio digital

processor 1A12A10 against input voltage surges from

the cable.

Change 2 2-20