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| ![]() 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
c.
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
of
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
a.
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
d.
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
b.
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
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