VCO 1A12A1, 1A12A11 and 1A12A18 Circuit Theory

TM 11-5820-695-35

same cable simulation networks are connected at each

board.

(1A12A10). This plug-in component is used only in the

asynchronous mode. In the synchronous mode, plug-in

component 683696 is used in chassis position A10.

2-40. VCO 1A12A1, 1A12A11 and 1A12A18 Circuit

This plug-in component does not have the

Theory

corresponding jumper connections and when it is in

place the switch is not connected. Terminals 1 and 6 of

Voltage-controlled oscillators lA12A1 and 1A12A11 are

switch S2 are connected to ground; terminals 3 and 4

sealed units that produce a frequency-stable

are connected to +5vdc (via terminal 20 of

squarewave timing signal at a frequency of 4608 kHz.

1A12A12A1TB2). The moveable arms, terminals 5 and

They are used only in the synchronous mode. In the

6, of the switch connect these voltages to pins 8 and U

asynchronous mode, voltage controlled oscillator

of plug-in component 1A12A10. In the asynchronous

1A12A18 is used. Its frequency is 9830.4 kHz. Chassis

mode, plug-in component 684092 is in use and the

position lA12A1 has a blank panel. The frequency can

internal jumpers route the input signal at pin 8 to output

be adjusted by means of a manual control to permit

pins N and 7, and route the input signal at pin U to

compensating for the frequency effects of aging. The

output pin R. Pins N, R and 7 of 1A12A10 then supply

output impedance is 470 ohms.

the required logic signals to input pins 4, 5, 9 and 10 of

1A12A9. The position of the ADDM TRAFFIC SELECT

2-41. Cable Digital Regenerator 1A1 2A2 and 1A12A

switch determines which inputs receive logic 1 and

13 Circuit Theory (fig. 5-30 and 5-30.1)

which logic 0. See paragraph 2-6b.1.

The integrated circuits used on cable digital regenerator

The power distribution bus on 1A12A12TB3

1A12A2 and 1A12A13 are shown functionally in figure 5-

connects the power supply voltages to the various plug-

30 for the synchronous mode and in figure 5-30.1 for the

in components in digital data modem 1A12. Capacitors

asynchronous mode. Figures 5-30 and 5-30.1 also

1A12A12A2TB1C5, C7, C9, C11, and C13 provide rf

specify each integrated circuit type.

Figure 5-24

filtering

the

power

lines;

capacitors

provides a circuit diagram for each type of integrated

1A12A12A2TB1C6, C8, C10, C12, and C14 provide

circuit used in Radio Set AN/GRC-144. The complete

filtering of low frequency transients. All the ground lines

functional description of cable digital regenerator

from each plug-in module terminate at the common

1A12A2 is provided in paragraph 2-5a (synchronous

ground bus on terminal board 1A12A12TB3. This bus is

mode) and for 1A12A13 in paragraph 2-5a.1

connected to chassis ground by a 4-inch braid and a

(asynchronous mode). Electrical operation of discrete

lug connected to the top rear of the case. Resistors

piece parts not discussed in paragraphs 2-5a and 2-5a.1

1A12Ai2A2R13 and 1A12A12A1R14 are isolating

is provided in a through below.

resistors that connect the modulation input voltages

(RVCOI and CVCO) to test points TP6 and TP7. The

Cable Simulation Networks.

The cable

signal ground for modules 1A12A1 and 1A12All is pin 3;

simulation networks consists of three 4-mile sections.

the case ground connection is provided at pin 7.

Selection is provided by plug P2. Resistors R1 through

Resistors 1A1l212A2TBlR5 through R9 are isolating

R7, capacitors C2, C3, and inductor L4 form on-4-mile

resistors that connect supply voltages to test points

network; R8 through R14, C4, C5, and L5 form a second

TP1

through

TP5. Resistor 1A12A12A1TB2Rll

network, and R15 through R21, C6, C7 and L6 form the

limits current from the +5v power supply when switch

third network. For example, if the cable length is /4

1A12A12Al')1 is in test position.

Resistor

mile, set the plug connections to Y4 mile. With the

1A12A12AlTB2R12 is not used.

arrangement three simulated V4 mile networks are in

series with the input 4 mile of cable providing a total

Indicator lamps 1A12A12A2DS1 through

equal to one mile of physical cable.

OS4 illuminate in response to the jumper plugs 'that are

inserted onto printed wiring boards 1A12A2 and

Amplifiers.

1A12A10.

The +5 volt power supply potential/is

connected to one side of the selected cable length

(1) Amplifier Q1 is a grounded emitter

indicator lamp by the jumper plug inserted into cable

voltage amplifier with a peaked response at 2304 kHz,

digital regenerator 1A12A2. The +5 volt power supply

due to tuned network R26, R22, C10 and L8. The signal

return is connected to the other side of the selected

input to amplifier Q1 is through

cable length indicator lamp by the jumper plug inserted

into radio digital processor 1A12A10. The selected

cable length indicator lamp will light provided that the

Change 1 2-79