Cable Digital Processor 1A12A4

TM 11-5820-695-35

lamp DS2 in 1A12A4 is lighted green and the alarm

R19 is applied through bias/current limiting resistors R20

signal output (radio repeater pcm failure, 1RRPFAIL) is

and R21 to the bases of transistors Q3 and Q4.

deactivated. If the retimed pcm signal is not detected,

Transistor Q3 is turned on and the ONOR output signal

the alarm circuit causes the green indicator lamp to go

is logic 0 (normal) because the +12vdc supply voltage is

out and activates

the failure signal (1RRPFAIL)

dropped across the collector load CR9 and R23

which is applied to alarm monitor 1A12A5 or 1A12A15.

Transistor Q4 also turns on, lamp DS1 turns on and

signal 1RPFAIL is logic zero (normal). If there is no

e. Orderwire and Direct Current Path (fig. 5-8 and

traffic activity, there is no voltage output from the

5-29). The orderwire portion of the from radio pcm and

rectifier and transistors Q1 through Q4 are all off.

orderwire signal (FRPCM) is recovered in radio

Signal ONOR is then logic 1 (alarm) and signal

amplifier-detector 1A12A7 The orderwire output signal

1RPFAIL is logic 1 (alarm). When Q4 is off, resistor

(RRW) from 1A12A7 is sent to orderwire assembly

R22 allows a small current to flow through lamp DS1 to

1A13 where it is distributed to the orderwire stations and

keep the filament warm. This reduces the current surge

routed back (cable ow in CCWIN) to af amplifier

in Q4 caused by lighting of DS1 when Q4 turns on

1A12A6 The amplified output of 1A12A6 (cable transmit

d. Cable Digital Processor 1A12A4 (fig. 5-8 and 5-

ow, CCTW) is applied to the primary of transformer

32) The radio-to-cable circuits portion of cable digital

1A12A12A2T2. The direct current path from the cable-

processor 1A12A4 is used only in the radio repeater

to-radio circuits is completed through the normally

mode of operation Cable digital processor 1A12A4

closed

contacts

the

fault

locator

relay

receives the retimed pcm (1RPCM) signal from radio

(1A12A12A2TBlK1) The fault locator relay is normally

control-comparator 1A12A9 and converts the 1RPCM

energized by a ground from the CABLE LOOP TEST

signal from standard logic levels to the levels required

switch (NORMAL position) or by a control signal (ON

by the input circuits of Transmitter,

Radio T-

R) from radio digital processor 1A12A10. When the

1054/GRC-144.

CABLE LOOP TEST switch is in NORMAL position,

fault locator relay Is energized; when the CABLE LOOP

(1) The retimed radio-to-cable pcm signal

TEST switch is in TEST position the fault locator relay is

(1RPCM) is applied through digital buffer 2 to level

deenergized. The position of the CABLE LOOP TEST

converter 2 and to alarm circuit 2 The level converter

switch determines the mode of operation of the cable-to-

(R9, R10, R11) converts the signal voltages to the levels

radio circuits of cable digital processor 1A12A4 (para 2-

required by the modulator circuits of Transmitter, Radio

5c), the radio-to-cable circuits of alarm-monitor 1A12A5

T-1054/GRC-144. The output signal, radio repeat pcm

or 1A12A15 (h below), and radio digital processor

(1RRPCM), is applied to the RADIO REPEATER

1A12A10 or 1A12A16. The effect of the CABLE LOOP

OUTPUT connector.

TEST switch on the operation of 1A12A10 or 1A12A16

(2) Alarm circuit 2 monitors the retimed pcm

is explained in c(3)(c) above; this information in relation

signal from the digital buffer. Operation of alarm circuit

to the relay to summarized in the following chart.

2 is similar to operation of alarm circuit 1, described in

paragraph 2-5c If the pcm signal is detected, indicator

CABLE LOOP

TEST

pcm

IA12A10 or IA12A16

switch position

traffic

ONOR

IRPFAIL

Relay

output signal

NORMAL ............... normal ................ logic zero ............ logic zero................energized ................... radio-to-cable pcm

Test........................ normal ................ logic zero ............ logic zero................not energized ............. cable loop-back

pcm

NORMAL ............... failed................... logic one............. logic one.................energized ................... no pcm

TEST ..................... failed................... logic one............. logic one.................not energized ............. cable loop-back

pcm

With the fault locator relay deenergized, the

pcm/dc/orderwire (FRPCM) signal from Receiver, Radio

resistor/capacitor/diode network on terminal board

R-1467/GRC-144 and the reshaped pcm signal

1A12A12A2TB1 is switched into the direct current path

(1RSPCM-2) from 1A12A8. The function of 1A12A7 is

and provides fault localizing information to Multiplexer

to recover the orderwire signal from the FRPCM signal

TD-204/U at the other end of the cable system.

(that is, eliminate the pcm component) and provide an

amplified orderwire signal as output The basic method

f. Radio Amplifier-Detector 1A12A7 (fig. 5-8 and

used to accomplish this purpose is to

5-35) Radio amplifier-detector 1A12A7 receives the

Change 2 2-20.2