I recently acquired this mystery military cassette recorder that dates from about 1979.
It features two independent analog microphone channels, two speeds and three optional power
inputs: 115VAC, 230VAC and 28VAC. Unfortunately, I cannot test it because the I/O path
is provided by an unmarked 25-pin foot connector, 6-pin power connector, and
12-pin audio connector. It would be very difficult to trace these pins.
The National Stock Number (NSN) was 5835-01-092-5311. I think the original procurement was
in 1979, and later in 1987 a manufacturer offered to produce forty more machines for $4000/each.
Also, this recorder was part of a training system identified as follows:
TRAINING SYSTEM,ELECTRONIC WARFARE AN/ULQ() 6910-01-070-7456
PO 8-0146 DESIGN CONTROL REFERENCE: PO 8-0146
I no longer have this recorder and never found a schematic.