[GreenKeys] Western Electric Bell System Mobile

[Geoff Fors]

Finding lots of interesting stuff here, I have just joined the list.

Duncan beat me to it, but further to the discussion of the Bell System
marked mobile receiver which Derek asked about, I can expand on this subject
a bit.   Some of the info below duplicates Duncan's message.   I am in the
process of putting together the mother of
all Bell System Mobile Telephone History web sites, but as it isn't ready
yet, here is some information:

The receiver shown does indeed look very much like a GE Pre-Progress low
band receiver, but if you look very carefully, you will see that it isn't!
GE receivers had green-painted covers with no louvers, not to mention a huge
red "GE" emblem.  This one is a Western Electric 38A VHF FM receiver
developed in 1945 primarily for the MTS car telephone system which the FCC
finally approved in 1946.  It was made by Western Electric and is a
miniature tube, updated version of the larger Type 28 and 28A VHF receivers
which they were making before the War for police and coastal/harbor
radiotelephone use.  The example in the
Derek's photo is missing the rotary stepper wheel decoder, which was covered
with a clear glass dome.  This was WE's last in-house mobile radio, as all
later car telephone equipment was supplied by GE and Motorola with added KS-
numbers by Western Electric.  There was also a companion Western Electric
Type 38 transmitter.  When the two were put together, it became the Type
238A mobile station.  There was also a Type 39A receiver (low band) and its
companion 39 Series transmitter.  Either of these setups used the Type 41A
under-dash control head, which stored the handset in an odd pocket on the
bottom half.  They were push-to-talk half-duplex operator assisted systems.

The first public Bell MTS car phone system went on the air in St. Louis in
June, 1946, on 152 MHz and was part of the "Urban" system (VHF high band.)
Shortly afterwards the "Highway" system went on the air in Green Bay,
Wisconsin in August, 1946 using 35 MHz channels (cars transmitted on 43
MHz.)    The Highway system followed the major land transportation routes
and was designed for use by truckers and that sort of thing.  Urban was as
its name implies.

The original low band channels were:  ZO, ZM, ZF, ZB, ZA, ZH and ZL.
The original high band channels were:  WJ, WR, JL, JP, JR and JS.

At first, equipment was generally single channel and tied to its home area.

After the FCC mandated narrow band changes in 1963, there became 11 USA high
band channels, namely: JL, YL, JP, YP, YJ, YK, JS, YS, YR, JK and JR.  The
low band channels became ZO, ZF, ZH, ZM, ZA, ZY, ZR, ZB, ZW and ZL.  Low
band remained half-duplex MTS and high band became a mixture of MTS, IMTS
and IMTS systems operating in the manual mode (still operator assisted.)

The first GE and Motorola two-piece equipment sold to WE specs had an
external decoder in a small metal case, the Type 106A Selector Set.  Later
one-piece sets made by GE had the decoder built-in, a Secode product.

I am still looking for a lot of this stuff for my collection and "virtual
museum" which will be on the web site.  Much of it was owned by the Bell
System and only leased to subscribers, so when it was pulled out, it wound
up being destroyed.  I will eventually have .pdf downloads of vintage Bell
System channel maps, manuals, articles and so forth available.

Regarding IMTS, although it was available in 1964, it did not see widespread
adoption on a national basis until the mid 1980's.  California, which
operated one of the largest mobile networks in the world, did not switch to
IMTS until late 1982.
Non-Bell affiliates (such as Con-Tel) used competing systems such as "Dial,"
"Identified Dial" and "Pushbutton Dial" rather than IMTS but still used the
Bell System channel block.  Private companies, called Radio Common Carriers
(RCC), had a block of 7 separate VHF high band channels and did whatever
they pleased, there was no standardization.  Most RCC's were half duplex
push to talk operator-assisted setups.

Sorry to be getting a bit off the RTTY topic, but I noticed that more than a
couple list members seem to be interested in this subject!

Geoff Fors
WB6NVH
Monterey CA