KX- TA624 Ext. 100 only speakerphone works

[telemarksman]

I was at new customer yesterday.
Reception Ext.100 having incoming call pickup issues. Cannot pick up calls, except for speakerphone.
Do not hear anything on handset. Yet when same exact phone is switched to different KSU jack port problems go away.
Plugged in three different phones Jack 01 Ext. 100. All had same symptoms.

Went to 408 all lines enabled.

Took phone to KSU port 1 same problem.

Thoughts?

alwayslearning

 

[bigglesnz111]

Headset mode enabled on phone , or handset plugged in to headset port on the phone
Been there done that..

 

[telemarksman]

The headset port is a mini RCA type female plug. No headset plugged in.

The installation manual and user manual state there is no programming for headset.

The phones are KX- T 7731B

alwayslearning