Computer Cassette Interface, Sol-20.
 

Recently I have been repairing and investigating the cassette tape interface in my Sol-20 computer. This is essentially the same as that used in Processor Technology's CUTS board and system, used in other S-100 computers too.

The article describes how it works. Also on the last few pages there is information that might help regarding a problem that crops up with the Sol-20's connection to the tape deck's remote input jack , which causes the small DIL relay's in the Sol-20 to fail (contacts stick closed), the reason for this, and the solutions. PT had one solution, but it was not ideal.

http://worldphaco.com/uploads/The_SOL-20_tape.pdf