Instruction manual

Adjustment Procedures
88 025-9416
TRUNK C
TRUNK D
LINE ANS ACT LINE ANS ACT
ANA PTT DIG PTT BUSY
GROUND
TRUNK D
TRUNK C
MODEL 640 DAPT XTRA
AGC KILL
FROM TEL
BAL R
BAL C
AGC KILL
FROM TEL
BAL R
BAL C
A
B
Figure 51. Trunk Card Level Adjustments
q
8. Set the meter range for 3-5 V
AC
.
q
9. Connect a buttset or equivalent high impedance monitor to the appropriate trunk.
q
10. Dial into the trunk (using any touch-tone phone) by way of the local telco CO.
q
11. Verify that the line under test is the same line dialed by monitoring the line for voice
on the buttset. (Speak into the telephone and listen on the buttset.) If no audio is
heard, redial to access the correct trunk.
q
12. Press and hold down one of the telephone’s touch-tone keys. (‘A’ transmits the
highest and lowest DTMF frequencies - 697 and 1633 Hz. If the phone does not have
an ‘A’ key, ‘3’ is the next widest tone pair - 697 and 1477 Hz.)
q
13. Set the AGC KILL switch to the kill position (toward the rear of the chassis). The
figure above shows the location of the AGC KILL switch and the potentiometers. Do
NOT kill the gain control until ready to make actual adjustments, as DTMF decoding
usually does not work with this setting.
q
14. Adjust the FROM TEL pot until the voltmeter reads 3.0 V
RMS
± 0.25 V
RMS
.
q
15. Set the AGC KILL switch back to the normal position (toward the front of the
chassis).
q
16. Verify that the FROM TEL DTMF level is ≈ -8 dB (435 mV
rms
) with the gain control
active.
Note: This tunes the knee of the AGC circuit for optimum operation.
q
17. Hang up the telephone and terminate the call.
The FROM TEL adjustment is complete.