5835-99-943-8232 Voice Operated & Remove Switching Unit for Recorder Output R.L.H.

Front view

This is what it looks like. As to what exactly it is and what it interfaces to or how it works -- your guess is as good as mine. Comes from 1963 though, looks like.

Inside view

It has an ECC83 and a relay and some other components. And that is all I can tell you about this thing.