I have a CTX100 phone system that has been working great for at least 10 years. All of a sudden I am having issues picking up a ringing line. Since it just happened I will give an example. My phone just rang. I picked it up and said hello. Although the light on the phone looked like it was picked up, the caller did not hear me. I quickly hung up and picked up another extension. Then the caller heard me. Any ideas?

Sure sounds like the phone.

The problem has happened on more than one phone. It is not the cord. I just unplugged the phone system and plugged it back in. I thought that might help.

What model phone? Some Toshiba sets were known to have hookswitch problems as they aged.

It is the DKT3020. Years ago I had a problem with a 2000 series hook switch.

When you picked up was your phone still ringing? Ringing line pick up would be the only other thing I can think of other than the hookswitch. My Toshiba days were over before the 3020 came out so I don't know if it had issues as well.

The phone stopped ringing when I picked up. The caller could not hear me and I could not hear the caller.

Pretty sure it is the hookswitch. One cct in the hookswitch controls the data and another cct deals with the audio. I have seen a bad hookswitch cause issues with both ccts.