Could you clarify whether you want the phone conversation to go through the mixer or you want to connect the phone to the phone line in a standard way and simply record the sent and received voices? Are you hoping the booth microphone (model?) could replace the phone handset microphone during the conversation?

It's a tricky area to get both right electrically and stay legal.

Thanks for the super fast reply, "Boswell"! Booth mic is a Neumann TLM 103, btw. If there is a way to route the call through the Mackie board and/or the Gentner Micro-Tel box so that I just wear my booth headphones and speak to the client through the Neumann, that's ideal. And: I don't need to record the the listener, if that helps.

If you're in that price range, you might also consider this unit from JK Audio.

The balanced XLR inputs and outputs would be of some value to me, vs. the Gentner.

Thanks, dvdhawk.... I already own the Gentner... but maybe I could sell it and pick up the JK Audio unit if that would turn the trick easily.

Then I'd take the example from the manual, for Recording Interviews, and add your mic-pre between the mic and the mic input jack. Then rather than going out to a tape recorder as shown, I'd take that Aux Out to your Mackie mixer. (Making sure I was using a shielded, mono 1/8" to 1/4" cable) At that point you can plug your headphone into the Mackie, or into the Gentner - whichever you prefer.

Thanks again, dvdhawk. I will give this a shot and advise back. Much appreciated!