Выражение встречается в следующем контексте:

Заранее спасибо
The Talk-Forward Microphone in the front panel of the audiometer is
switched off automatically when by connecting the headset.
If THE AUDIOMETER was delivered with a Patient Talk-Back Microphone,
insert it’s plug into the rear side connector “Microphone Patient”. The VU Meter is used to adjust the sensitivity of the inputs for the line-in and for the
external talk-forward and talk-back microphones