Troubleshooting Apartment Intercom System

Entire System Dead
If power LED is not illuminated, check for 16 VAC at transformer secondary and 120 VAC at transformer primary. If LED is illuminated, review field wiring and perform direct test using one of the apartment stations to eliminate field wiring.

No Talk
Check wiring to terminals 1 and 2, and check whether wiring to entrance panel speaker is shorted or open. Suite station can be swap tested with another working unit.

No Listen
Check wiring to terminals 1 and 3, or for short between terminals 1 and 2. Check to see if wiring to entrance panel speaker is shorted or open. Suite station can be swap tested with another working unit.

No Door Operation
Check wiring to door release for shorts and opens, or for defective door release. Confirm that shunts are properly set for door release type and that connections to appropriate output have been made. Check wiring to terminals 2 and 3, or 1 and E (depending upon suite station type).

No Call Tone
Check wiring to terminal Z or ZW to entrance panel, related entrance panel call buttons, and suite station X terminal. Suite station can be swap tested with another working unit. Excessive Hum or Distortion Check whether wiring is installed too close to electrical wiring or electrical devices; amplifier installed too close to transformers or other electrical devices; twisted pair wiring not used as required; or amplifier voice volume set too high.

Radio Interference
Connect G terminal from amplifier to electrical ground. Note: This connection is not shown on the wiring diagram, since the situation is not always improved by adding it. If the problem persists, consult the factory or service representative.

Oscillation (feedback or howling)
Reduce the voice volume until oscillation is eliminated. If oscillation stops when the call tone wire is removed from ZW, set entrance tone (SW3) to the OFF (left) position.

Signal Flow and Theory of Operation for PK543A Amplifier and Apartment Intercom System
The following example describes an apartment intercom system using a PK543A in conjunction with a 4-wire suite station. Refer also to Figure 5 on page 8.

Call Button
Pressing a suite station call button on the entrance panel routes the call tone from the Z or ZW terminal on the PK543A to the X terminal (tone in) on the associated suite station. This signal then passes through the speaker and returns to the PK543A via the 1 terminal (audio common). If the warble tone is in use and the entrance tone feature is active, the tone will also be heard through the entrance panel speaker when the call button is pressed.

Talk Button
Pressing the talk button at a suite station connects the suite station’s internal speaker to terminals 1 and 2 of the PK543A, which serves as an audio input to the amplifier. The audio is then amplified and sent to terminals A and G, which are connected to the entrance panel’s speaker (speaker mode).

Listen Button
Pressing the listen button at a suite station connects the suite station’s internal speaker to terminals 1 and 3 of the PK543A, which serves as an audio output from the amplifier. This allows the suite station to receive the amplified audio being received by the amplifier on terminals A and G from the entrance panel speaker (microphone mode).

Door Button
Pressing the door button at a suite station creates a closure between terminals 2 and 3 on the PK543A. This state is sensed by the amplifier and causes the door release to be activated (output specifics are based on PK543A settings). This state is also triggered by shorting terminals 1 and E as is typically done by a postal lock.