CPI Communications MR200(N) Series - Manual (Page 4)

4.0 Tuning
The MR200N termination panels 2175 Hz notch and bandpass filters and line balance adjusters have been fac-
tory 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 (J3 or J4 pins 3 & 4)
+12 volt power to J4-1
Ground to J4-2
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 E2-16. Set
generator for 1500 Hz, at 2 Vpp. Terminate J3 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 E2-16 and ground
+13.8 volt power to J4-1
Ground to J4-2
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 J3, connect a RMS volt
meter to the leads of L3 and L4. 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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