Solution
When the USBTap is connected to the headset/handset, the
flat phone cable between the two devices expects speaker
and mic. The tap expects the inside 2 wires as speaker and
the outside 2 wires as microphone. The mic wires are negative
or positive. If the phone is wired different it could be a
polarity issue.
We use the inner pair(speaker) outer pair(mic) standard.
If you have the proper tools try swopping the 2 mic wires
(on both ends).
This has also been noted with the:
1.Plantronics Supra Plus P251N/A P/N 3683-01 headset.
2.Panasonic KXT-GA110EX - polarity issue to be confirmed.
3.HYBREX DK serie phone.
Cld= CALLED