This page submitted by Steve
Shepard who put this item up for auction on eBay.
Click on hyperlinks below to view photos of the unit.
"Of all the strange things that have been
manufactured by Western Electric, this extremely rare "Mirrophone 213-A
Reproducer Set" has to be one of their most unusual. It's called a
Mirrophone (that's the correct spelling). When I found this at a recent estate
sale, I thought the
label said
"microphone", and assumed that it was some kind of public address
amplifier. It's not. Instead, it's a one-minute continuous loop wire
recorder/playback machine. It may have been used as a voice training instrument.
It was made by Western Electric for its subsidiary, Electrical Research
Products, Inc. (ERPI). Notes found with it indicate that it was made no later
than 1944. I have no other documentation.
In operation, one plugs a microphone (not
included) into the input jack on the front of the instrument and sets the
controls
to the "record" mode. The correct recording volume is set with the aid
of the built in
"magic
eye" cathode ray indicator, which displays the amount of modulation
present. A message of up to about a minute in duration may be recorded. After
recording, the controls are switched to the playback mode and the message will
be played back continuously, either through its internal speaker or to an
external amplifier (not included). There is a
motorized
pointer, just below the Magic Eye, that rotates once per minute as the
message is being recorded or played back. It indicates the time remaining/time
elapsed of the message. .
There are many unusual and unique features of
this device. As near as I can estimate, there is a seventy-seven foot endless
loop of
metal recording
wire, wound 28 times around the spools and wheels of its
transport
mechanism (for another view click
here).
The entire length passes over the unit's
record/playback
head once per minute. This works out to be pretty close to a wire speed
of fifteen inches per second: The wire really flies around its circuitous path
at a good clip. You may be familiar with wire recorders of the forties and
fifties that preceded today's tape recorders. Those reel-to-reel recorders used
wire that was round in cross section. In contrast, the Mirrophone's wire is
flat, like the tape in a modern tape recorder. Its approximate dimensions are
0.05 inch wide by a few thousandths thick (maybe about 0.003 inch). I did not
want to risk damaging the wire with a micrometer, so did not take an actual
measurement. The recording and pickup
heads are very primitive. They look very much like small solenoid coils.
Several features lead me to believe that this may
have been a prototype or of very limited production. The entire cabinet is made
of wood, except for the metal back panel. There is a brown wrinkle-finish paint
applied to the sides and top, and gloss brown paint on the front panel, both of
which give the impression of a metal cabinet. Also, if you look at the close-up
pictures of the front panel controls, you will see position markers around the
"Volume", "Repeat/Record", and "Timer" knobs.
These are simply little brass round-head nails pressed into the wood. Surely a
high-production machine would have been made differently. The low serial number
(201) is another indication that there may not have been many units produced.
This is not a hi-fi however, and the sound
quality is inferior by modern standards. The
Magic
Eye tube is bright and functions properly. I used a magnetic microphone
to do my recording, but I believe that a ceramic type would work as well. I
don't see why any other audio source could not be used as easily. The four tubes
used are 6X5, 6V6GT, 6B8, made by RCA and Philco, and the
6E5
Cathode Ray Indicator, made by Emerson.
It still has a Railway Express shipping label
attached, over which has been placed a shipping label from the Mountain States
Telephone and Telegraph Company (click
here
for photo).
I received an email from Dave D. referencing a
book that appears to exactly describe the Mirrophone. The book is "Magnetic
Recording" by S.J. Begun (Vice President and Chief Engineer, the Brush
Development Company), Rinehart and Company, NY, 1949.
Here are some excerpts from page 159 of that book (there is a also a schematic
and a photo of the device) :
"The Mirrophone... was manufactured by the
Western Electric Company in the beginning of 1940 and was intended primarily
as a voice-training device and for use in the telephone system for
weather-announcing purposes.
"The recording medium consisted of 0.050 inch wide Vicalloy tape in the
form of an endless loop, supported on three rollers... The medium was wound
over the three rollers in a manner somewhat similar to a reversible threaded
screw so that no crossover path was necessary. A spring-biased pulley
maintained the medium at constant tension. A belt drive was employed, driving
one roller to propel the tape.
"The recording time of this instrument was about 1 minute, and a time
indicator on the front of the panel informed the user when to switch from
recording to reproducing. Direct-current bias was used. The instrument covered
a frequency range of from 100 to 5,000 c.p.s. and had a dynamic range of about
40 dB."
There is also a small, blurry photo and passing
mention of the Mirrophone in Appendix A of "Magnetic Recording
Handbook" by Marvin Camras (Van Nostrand Reinhold Co., 1988). The photo
credit is "Wireless World" magazine, Feb 1942, so it's possible
there's more info there (or possibly not; some of the old magazines had only
short blurbs about amazing new devices).
Uncrated, the Mirrophone weighs 60 pounds. It
measures 15-1/2"H x 19"W x 13"D. The shipping/storage box weighs
35 pounds, measures 22"W x 22"W x 16-1/2"D."
Other photos not linked from text above:
Electronic
(tube) circuit
Corner
view of unit
Internal
backside view
Left
side view
Power
switch and label
Magic
Eye in "off" condition
Heads
- Close-up 1
Heads
- Close-up 2
Heads
- Close-up 3
Speaker
grill
