Heathkit T3 Visual Aural Signal Tracer

[Tubejunke]

I have one of these units and seem to have got it in working condition. By that I mean that I replaced all four electrolytic capacitors that were in a 4 section can and got rid of one heck of a "hummer."

I have the user manual and I am able to use the RF probe to hear signals at different points in a radio through the on-board speaker. My question really is what is an audio probe? The instructions don't picture one. Is it simply a shielded cable that plugs into the headphone jack on the unit and would have alligator clips or something on the end to connect to the secondary of an audio output transformer or is there some greater purpose for this that I am failing to understand?

I would like to know and understand all of the functions of what seems to be a neat piece of vintage equipment. If anyone here has one, please fill me in on the uses of it other than simply using the RF probe to trace signals through stages.

Thanks!