[jpeterman]

My understanding is that this guy was a telephone "phreaker" (hacker enthusiast) and I gather he traveled a lot and would use pay phones and record them as he did.

The "tapes" are him narrating over these old tapes many years later explaining what he was doing. Much of it is him dialing various numbers and listening to the beeps/boops/kachunks and explaining exactly what is happening technically to route the call.