National Multiplex data cassette tape drive

From: William Maddox <wmaddox_at_pacbell.net>
Date: Tue Aug 24 19:09:47 2004

Years ago, I owned a data cassette drive made by a
company called National Multiplex, presumably long
defunct. It was obviously a modified audio cassette
recorder, but in which the internal electronics had
been completely replaced. Unlike the prevailing
standard for cassette-based data storage on micros
in that day, this drive used saturation recording
(NRZI, I believe) instead of a modulated audio
carrier.
It was a very functional replacement for a paper tape
reader/punch, and ran up to 9600 bps using hi-fi grade
audio tapes.

I would be interested in locating one of these beasts
to replicate the setup I had on my IMSAI before I sold
the drive years ago. The drive came with schematics,
and as far as I remember, the circuitry was rather
simple -- a couple of op amps and a few gates.
Alternately, if I can locate a copy of the drawings,
I may attempt to reproduce the design using a
contemporary audio cassette mechanism.

Has anyone ever seen one of these?

--Bill
Received on Tue Aug 24 2004 - 19:09:47 BST