User's Manual

Testing & Troubleshooting

Push-button Operation

Apply mains power to the control unit and turn on at the fused isolator switch.

When a push-button is pressed the associated speech-circuit on the relay board (RLX) should

engaged for 60 secs then drop-out. Each circuit on the relay board has an led indicator

adjacent to the telephone terminal block. Test each button on the entrance panel in turn

confirming that the associated LED only comes on, and wait each time for it to clear.

In the event of problems it can be verified that the equipment is operating correctly by

temporarily disconnecting the push button connections and all other external

connections then use a short length of wire to simulate each button according to the matrix

shown in diagram 2 or diagram 5 (eg to simulate button 1, momentarily short 'A' to '1').

Assuming that the equipment is functioning correctly any problems must be traced to the push-

buttons and/or their associated wiring.

Testing the Telephones

Having established that each entrance button is correctly engaging its associated speech circuit

on the relay board(s), it is now necessary to test each telephone in turn:

1. First check the operation of the mute facility by pressing the 'PRIVACY' button on the

telephone and observing that the red LED alternatively lights and extinguishes. If the

LED does not light then check the telephone cabling (in particular lines V & O, V is +12

V DC and O is negative). Check also the associated fuse on the relay board; this fuse

will only blow if there is a short-circuit on the cable; under no circumstances replace this

fuse with an incorrect type or rating (it is 200mA, 20mm, Quick Blow). When the mute

circuit is operating leave it in the OFF state (ie LED off).

2. Call the telephone being tested by pushing the appropriate button on the entrance

panel; it should sound loud and clear. If there is no buzzer operation verify again the

relay board LED and fuse and then check the 'I' connection to the phone for possible

faults.

3. Once the telephone has been successfully called it should be possible to converse with

the entrance. If there is no speech available in either or both directions check firstly the

speech unit volume controls and secondly the cable connections;

The Model 51 Speech Unit has 2 volume controls:-

VOL A: controls the speech level from phone to panel.

VOL B: controls the speech level from panel to phone.

Initially set both controls to mid-position and adjust each in turn for optimum speech

clarity. It should be noted that if either or both controls are turned too high there will be

a howling sound caused by acoustic feedback. This problem may also be induced by