Problem: Red SHORT LED illuminated
Cause 1: Short or overload on that channel due to a shorted or miswired cable.
Solution 1: Remove the intercom line cables one at a time from the system until the faulty line
is located. (The red Short LED will then turn off.) Check for shorts between pins 1
and 2 or improper cable wiring. Once the short is removed, the MS-232 will reset
automatically and power will come back up within several seconds.
Cause 2: Defective remote station.
Solution 2: Check the remote station and replace if necessary.
Problem: Both red SHORT LEDs are illuminated
Cause 1: System is overloaded.
Solution 1: Remove the intercom line cables one at a time from the system to help determine
where the excess current requirements lie. Re-evaluate the system current needs.
Cause 2: Short in multipair cable.
Solution 2: Remove the intercom line cables one at a time from system until the faulty line is
located. Check for shorts between pins 1 and 2 or improper cable wiring.
Problem: Hum or buzz in system
Cause 1: Inductive pickup caused by close proximity of this main station or connected re-
mote stations to power lines or transformers.
Solution 1: Relocate the offending unit.
Cause 2: 10 Ohm chassis ground resistor is open.
Solution 2: Check the DC resistance for 10 Ohms between the chassis and pin 1 of any inter-
com connector.
If this condition occurs, it is because the system ground came into contact with something that
was "HOT" with respect to the power supply earth ground. Carefully check the system ground
and AC distribution in the area.
WARNING
: THIS IS A POTENTIALLY DANGEROUS SITUATION. A SHOCK HAZARD
MAY EXIST BETWEEN A REMOTE STATION HEADSET AND GROUND.
Problem: System feedback (Acoustical)
Cause 1: Listen Level control at this station or a remote station is set too high.
Solution 1: Adjust.
Cause 2: Sidetone Null control at this station or a remote station is not adjusted correctly.
Solution 2: Adjust. Refer to the procedure in the Front Panel section of this manual.
Cause 3: Channel unterminated.
Solution 3: Set the MS-232 termination switch for that channel to the ON position.
Cause 4: A headset extension cord was used.
Solution 4: Headset extension cords are not recommended.
Problem: Excessive crosstalk
Cause 1: High DC resistance in ground return.
Solution 1: Use heavier cable; add additional conductor(s) to ground return.
Cause 2: MULTI-CHANNEL cable pairs are not individually shielded.
Solution 2: Replace cable with individually shield pairs.
Cause 3: Headset cables are not wired properly or shielded properly.
Solution 3: Correct wiring. Use headsets with properly shielded wiring.
Problem: Program signal sounds distorted.
Cause: Overload of Program Input circuit.
Solution: Reduce Program Input level or reduce the gain of the program signal at the source,
such as an audio mixer.
Clear-Com MS-232 Two-Channel Main Station
10
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General