These machines were used for radio & TV station program logging (used to be an
FCC requirement), and for law-enforcement telephone logging. The ones I've
seen used 1 or 2 inch tape running at 15/16 ips or less (recording) and could
record a dozen or so separate, parallel channels via a nightmare-ish rotating
head assembly. You could play back at 2x or 3x and usually hear intelligible
voice. You turned up the speed then dialed down the pitch. Not real sure about
the physics, but I suspect it was a hetrodyne system of some kind.

Hi,

I've heard talk before on this group of a machine with a rotating
audio head that could vary the speed of the recording without altering
the pitch. Apparently it would vary the head's rotation speed in sync
with the tape speed so that the pitch stayed constant. I suppose it
was an early form of analog over-sampling...

A*s*i*m*o*v

... A stereo system is the altar to the god of music.



webpa