Telex MCE325 - Manual (Page 50)

4-12 C S I - 2 0 0 U s e r I n s t r u c t i o n s
ISO Test
1 Set DIP switch DS3 to off (two-channel, two-wire mode).
2 Set DIP switch DS5 to on (talk muted during ISO).
3 Set all TALK and LISTEN buttons to on.
4 Connect a 100 ohm resistor from the ISO input (J22 pin 12) to circuit common (J22 pin 10).
Observe that the MIC ON LED turns on and the channel 1 and 2 TALK buttons turn off.
5 Remove the 100 ohm resistor across the ISO input.
6 Reset DIP switch DS3 to on and DS5 to off.
Remote Mic Switch Test
1 Set all buttons to off.
2 Connect a 100 ohm resistor from the remote mic switch input (J22 pin 25) to circuit common
(J22 pin 10), and observe that the MIC ON LED turns on.
3 Remove the 100 ohm resistor.
Program Lockout Test
1 Set DIP switch DS4 to on (front panel setup lockout enabled).
2 Press and hold the CALL button for ten seconds, and verify that the MCE325 does not enter
program mode.
3 Reset DS4 to off.
Noise Checks
1 Connect a 150 ohm load across the dynamic mic input (J2 pins 1 and 2).
2 Connect an 8 ohm load across the speaker output.
3 Connect 51 ohm loads across the left headphone output (J2 pins 3 & 4) and right headphone
output (J2 pins 3 &5).
4 Terminate each intercom channel into 200 ohms.
5 Set the MIC ON button to on.
6 Set the SPKR ON button to on.
7 Set all other front panel buttons to off.
8 Set all volume controls to minimum.
Note: Noise measurements in the following steps were made using a 30 kHz low pass filter
with +20 dB of gain inserted between the AC voltmeter and the MCE325.
9 Set the CH 1-3 volume control to maximum. Measure noise across the left headphone output. It
should measure -44 dBu or less.
10 Set the CH 1-3 volume control to minimum and set the CH 2-4 volume control to maximum.
Measure noise across the right headphone output. It should measure –44 dBu or less.
11 Set the CH 2-4 volume control to minimum. Measure noise across the speaker output. The
meter should read –44 dBu or less.