<I remember CUTS, but someone else mentioned 88-ACR and I'd never Altair cassette interface which was narrow FSK at 300baud. The actual board set was called 88-ACR and was a mits sio with a modified modem board (tx/rx frequencies the same). bell 103 uses differet tones for TX and recieve so for modem use it was useless. It is however narrow FSK. Allison