[ICOM] RJ45 mic jack question

[John Geiger]

I see from the manual for the Icom 706 original that the AF out audio is
available from the mic connector, much like it is from the ACC connector.
The manual doesn't state, though, if this audio is fixed level or controlled
by the AF gain.  Does anyone know this?  I am trying to come up with a
simple AFSK/digital interface using only the mic connector (and VOX). Has
anyone designed one this way, or know of commercially available products
using the mic connector for both audio in and out?

73s John AA5JG