CPI Communications TTP(N) Series - Manual (Page 4)

4.0 Tuning
The TTP(N) termination panels 2175 Hz notch and bandpass filters and line balance adjusters have been factory
set. These adjustments have been “painted” and should not require readjustment in the field.
If it does become necessary to “retune” the panel, the procedure is as follows:
TX Audio notch filter
1) Connect: Signal generator (600 ohm) set at 2175 Hz. 0 dBm to phone line J2
+12 volt power to J1-2
Ground to J1-7
Scope probes to TP4 & TP5, set scope to X-Y mode
2) Adjust R21 until signal on scope is in phase (loop closes on scope).
3) Remove scope probe from test point 4 & 5. With scope in signal channel mode, connect 1 probe to TP6.
Adjust R16 to obtain minimum signal on scope. Adjust R21 to further reduce signal level. Re-check R16 then
R21. Notch will be approximately -58 dB.
4) Move scope probe to TP7. Adjust R46 to maximum signal on the scope. (This is the 2175 bandpass adjust-
ment.)
5) To set the balance, remove signal generator from phone line. Re-connect between ground and J1-6. Set
generator for 1500 Hz, at 2 Vpp. Terminate J2 with a tone remote or other suitable 600 ohm load. Move scope
probe to TP4 and adjust R100 for minimum.
RX Audio notch filter
1) Connect: Signal generator (600 ohm) set at 2175 Hz. 0 dBm to J1-6 & J1-7
+12 volt power to J1-2
Ground to J1-7
Scope probes to TP1 & TP2, set scope to X-Y mode
2) Adjust R8 until signal on scope is in phase. (loop closes on scope)
3) Remove scope probe from TP1 & TP2. With scope in signal channel mode, connect one probe to TP3. Ad-
just R13 to obtain minimum signal on scope. Adjust R8 to further reduce signal level. Re-check R13 then R8.
Notch will be approximately -58 dB.
5.0 Level Adjustments
RX Audio Adjustment
R101 controls the RX audio level to the phone line. With the phone line connected at J2, connect a RMS volt
meter to the leads of L1 and L2. Un-squelch the receiver so that continuous noise is present and adjust R101 for
0 dBm or 0.8 Vrms on the meter. If additional gain is needed to achieve 0 dBm, move jumper JP6 to short pins
2 & 3.
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