Fault in Specific Station Only, Symptom

5.2 Fault in Specific Station Only

Find the cause according to the following table if the fault lies with a specific station only, not with all stations.

Dialing can not be made at privacy off mode.

Specific key does not operate.

Calling tone can not be heard. Sound from the other party can not be heard.

Sound is not trans- mitted to the other party.

On dialing, noise is heard by the called party.

Sound of the other party is broken during call.

Immediately after the calling tone, the line switches to cancel, busy, dial tone, etc.

CHECK-ITEM		CAUSE
Replace the	*	Disconnection of both T & R Lines.
station and make	* T & R Lines are shorted.
sure that the
station is not
faulty.
Replace the	*	Fault in key board switch or matrix circuitry.
station and make	*	Fault in the dial generator. (Replace PCB
sure that the		board.)
station is not
faulty.
Same symptom	*	Short or open in R Line.
remains even if	*	Fault in LAU.
the station is
replaced.
Becomes normal	*	Disconnection of R Line or improper connec-
if the station is		tion of the station connector.
replaced.	*	Fault in LAU.
	*	Station fault.
Same symptom	*	Short or open in T Line.
remains even if	*	Fault in LAU.
the station is
replaced.
Becomes normal	*	Fault in MIC circuitry of the station. (Replace
if the station is		MIC or PCB.)
replaced.
Same symptom	*	One of T Lines is disconnected.
remains even if	*	Fault in LAU.
the station is
replaced.
Becomes normal	*	Fault in MIC element.
if the station is	*	Fault in T Line of the station.
replaced.	*	Low-frequency oscillation of MIC AMP.
		(Faulty bypass capacitor.)
Same symptom	* Adjust the volume control of station speaker
remains even if		if the room produces reverberation. (Lower
the station is		the volume.)
replaced.	*	Increase the gain of MIC AMP.
	*	Replace PCB after checking if MIC unit is not
		touching its case.
Same symptom	* One of R Lines is disconnected.
remains even if	*	Fault in LAU.
the station is	*	Station fault.
replaced.
Becomes normal	*	One of the R Lines is disconnected or the
if the station is		station connector is not connected properly.
replaced.