[EMI BTR 3]

.0036 inch is the diameter of recording wire. The first recording machine I ever saw was my dad's Webster-Chicago model 80 wire recorder, which I still have.

Speed is more or less 2 feet per second. The takeup drum on my machine is somewhere around 4 1/2" diameter and turns at about 110 rpm. No capstan, so the speed of the wire from moment to moment depends on how much wire is on the drum.

As an experiment, some years ago I ran a one hour spool (approx. 7300 feet of wire) all the way to the end, and then started another spool of wire over all of that for several seconds, just to hear how much faster the wire ran. What music I heard was just a half step sharper than normal, suggesting the speed at the end of an hour spool was about 6% faster than at the start.

Rewind speed on the W-C machine is something like 7 times the record speed, so an hour's worth of wire requires 8 1/2 minutes to rewind, provided it doesn't break/snarl at some point.

Usable frequency response is somewhere on the order of 70-3500 Hz. No HF pre-emphasis in record either, but does employ AC bias via the 6V6 output that in 'listen' is the small power amplifier.

About the only wire recorder I know of that had a capstan drive was Magnecord's first product, the SD-1, introduced in 1946. It used the same large-hole spools as the Webster-Chicago machines, but was intended as a studio-quality deck. AFAIK it was the only wire recorder with two speeds; frequency response was said to extend to nearly 10 kHz at the faster speed of 4 feet per second (48 ips).