Overall Block Diagram Description of Digital Data Modem 1A12

TM 11-5820-695-35

applied to the alarm circuits in 1A13 along with the

-6 vdc and +5 vdc voltages required to operate the

transmitter and receiver alarm signals to control the

circuits and indicators in Transmitter, Radio T-

CNTRL ALARM indicator and audible alarm.

1054(P)A/GRC-144(V).

2-4. Overall Block Diagram Description of Digital

c. Metering Circuits.

Signals from various

Data Modem 1A12 (fig. 2-1 and 2-1.1)

components in the T-1054(P)A/GRC-144(V) are

monitored at meter panel assembly 1A15A8. The

a. Digital Data Interface. Digital data modem 1A12

metering circuits consist of a meter selector switch and

interfaces the cable systems and Radio Set AN/GRC-

a meter. A signal is monitored by setting the meter

144. It has two modes of operation: synchronous (48-

selector switch to the appropriate position.

Meter

channel only) and asynchronous (48-channel or 96-

calibration resistors are provided for certain meter

channel). The complement of plug in components used

indications. The metering circuit also provides a test

depends on the operating mode as shown in the chart

position which allows component test lead monitoring.

below. In addition, when the 96-channel mode is used,

1.0 MHz low pass filter 2A3 must be replaced with 3.8

d. Power Supply Circuits.

Power supply 1A1

MHz low pass filter 2A17 for digital data interface.

produces regulated +28 vdc, +15 vdc, +12 vdc, -12 vdc,

48-channel

48 channel

96 channel

synchronous

asynchronous

(DDM)

Description

(ADDM)

1A12A1 (4608 KHz) .............

Voltage controlled oscillator.......................

1A12A17 ..............................

1A12A17

(Dummy Panel)................

(Dummy Panel)

1A12A2 ................................

Cable digital regenerator ...........................

1A12A13 ..............................

A12A13

1A12A3 ................................

Cable control-compactor ...........................

1A12A14 ..............................

1A12A14

1A12A4 ................................

Cable digital processor..............................

1A12A4 ................................

1A12A4

1A12A5 ................................

Alarm monitor............................................

1A12A15 ..............................

1A12A15

1A12A6 ................................

Af amplifier................................................

1A12A6 ................................

1A12A6

1A12A7 ................................

Radio amplifier-detector ............................

1A12A7 ................................

1A12A7

1A12A8(w/Y1) ......................

Radio digital regenerator ...........................

1A12A8(w/Y2)......................

1A12A8(w/Y2)

1A12A9 ................................

Radio control-comparator..........................

1A12A9 ................................

1A12A9

1A12A10 ..............................

Radio digital processor..............................

1A12A16 ..............................

1A12A16

1A12A11 (4608 kHz)............

Voltage controlled oscillator.......................

1A12A18 (9..........................

1A12A18

(9 830400 MHz)...............

(9.830400 MHz)

2A3 (10 MHz) .......................

Low pass filter...........................................

2A3 (1.0 MHz)......................

2A17 (3.8 MHz)

(1) In the radio receive direction (radio-to-

(2) the radio transmit direction (cable-to-radio),

cable), digital data modem 1A12 receives the combined

digital data modem 1A12 receives a combined

pcm and orderwire signal from Receiver, Radio R-

pcm/orderwire/dc signal from the cable system. Digital

1476/RC-144 and separates the pcm signal from the

data modem 1A12 separates the two signal components

orderwire signal. The pcm signal is processed by digital

and loops the direct current back to the cable output

data modem 1A12 into a form which is compatible with

terminal to complete the closed circuit direct current

the cable system. This is explained in (3) below. The

path. The extracted pcm signal is processed by digital

recovered orderwire signal is applied to orderwire

data modem 1A12 into the form required for radio

assembly 1A13 for further processing. Before applying

transmission. This is explained in (3) below. The from

the processed pcm signal to the cable, digital data

cable orderwire signal is applied to orderwire assembly

modem 1A12 recombines it with the orderwire signal

1A13 for further processing.

from orderwire assembly 1A13. There is a continuous

direct current path between the cable input terminal of

(3) In the synchronous mode, Radio Set

digital data modem 1A12 and the cable output terminal,

AN/GRC-144 transmits and receives information in a

48-channel pulses code modulation (pcm) system. The

so the output signal is comprised of pcm/orderwire/dc.

signal is in the form of a serial stream of voltage pulses

(bits) representing the

Change 6 2-7