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iC BLOCK DIAGRAM
1¢3 PQVISC77655S
IC1, 2 POVIBA6565A
TRANSMIT
ATTENUATOR
ATTENUATOR
|
CONTROL
TRANSMIT CANNEL
TRANSMIT
LEVEL
DETECTOR
TRANSMIT:
RECEWE
COMPARATOR
RECEIVE
LEVEL
DETECTOR
Vex
REGULATOR
Fig. 9
Fig. 10
RECEIVE
ATTENUATOR
ADJUSTMENT
Perform the following adjustment after replacing C3 and VR2.
Test Equipment:
| Loop Simulator
RC Oscillator
VTVM
Please refer to Circuit Board and wiring Connection Diagram
which is located test points (¥).
Preparation:
pa
Schematic Diagram of Loop Simulator
1. Sat the unit's controls as follows:
A, SP-PHONE SWITCH—"ON""
B, MUTE SWITCH—''OFF"
C. VOLUME
CONTROL—
MAX"
2. Connect Test Points
V-Y.
3. Set the variable resistor of the loop simulator to maximum
resistance (fully counterclockwise).
4. Connect the unit to the loop simulator.
5. Make ail adjustments in a quiet room.
. After adjustment are made, disconnect the Test point W- WY.
VARIABLE
RESISTOR
06-5000
ita 48 V OC power supply +s not avavabie a
20. VOC power: suppyy can De suosttuted
Mowever
the sacaple resistor 10 $0000)
must be $4! 100 onms
. Set the loop simulator selector switch to "TX".
2. Connect the RC Oscillator to Test Point YY ~ ® , and connect
an electrolytic capacitor (50 V, 1 pF) as shown below.
3. Set AC Oscillator to 1 kHz, -- 56 dBm.
-yt
at
v
3)
1kHz,—-56dBm 50V 1 uF
:
iy
4. Connect the VTVM to Test Point
YY (—-)-—
YW (+).
. Adjust VR2 for a reading of —23 dBm, +0.5 dB, on the VTVM.
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