Privateline.com's Telephone History
Pages: Pages:
(1)_(2)_(3)_(4)_(5)_(6)_(7)_(8)_(9) (10)
(11) (Communicating)
(Soundwaves) Next page -->(Life
at Western Electric) next
page -->
Mobile Prefixes / Landline
Prefixes / London
Exchange Names in 1916
Editor's note. This page discusses early mobile telephone
prefixes. If in fact they existed. The chart Geoff refers is
linked to below, a Bell System list of approved prefix numbers
and names:
Hi Tom-
Yes, that chart appears to be correct. http://ourwebhome.com/TENP/Recommended.html
As you know, until IMTS came around, mobile numbers had no
direct dialing capability and only 5 digit numbers, so a mobile
number was always prefixed by its home channel, thus:
JL 5-5575 or YK 4-3378
To reach a mobile phone, you had to dial the operator and
then ask for the mobile operator in the city of registry of the
mobile phone. Then you had to ask the mobile operator to ring
the mobile, by telling her the mobile number, such as "
JL 5-5575 , city of registry Los Angeles." A few years before
Pac Tel switched over to IMTS, they were telling people to start
using the area code rather than the city of registry. So they
were expecting you to ask for "Area Code 213, JL 5-5575."
The mobile terminalwould out-pulse 5 digits, i.e. 5 5575. Theoretically
that could ring more than one phone, if a foreign mobile with
the same number were in that area. In other words, an Alabama
mobile with JL 5-5575 would also ring as there was no way to
identify the city of registry with a 5 digit system. IMTS, as
you know, was a 7 digit system. The IMTS phone was programmed
with the area code then the last 4 digits. The prefix was not
part of the ANI string. In other words, my mobile number of (408)
679-5575 was programmed into my mobile as 408-5575. As a hacker,
I had a devil of a time figuring that out when I was experimenting.
Even when I signed up for service, Pac Tel never said a thing
about it.
There were 11 channels, as identified on the channel buttons
of your Livermore attache phone. Each would originally have been
a mobile # prefix. I see 57 is the numeric equivalent of channel
prefix JR, but also JS and JP. Looking at the chart, I see 97
is also reserved, and would represent channels YR or YS or YP.
The VHF channels start with a J or a Y so you would also need
to reserve prefixes 55 and 95.
But I don't see any point in ever having reserved those exchange
prefixes for mobiles, since there was no way they could ever
have been dialed direct in an MTS manual system. You always had
to ask for a mobile operator, and then say the channel, rather
than the prefix. I think the reservation of those exchange prefixes
was part of an early idea that someday they would have direct
land to mobile dialing even in MTS phone systems, which never
happened.
On another more arcane subject, those decoder gear wheels
in the earliest mobile phones were not capable of using certain
number combinations by reason of mathematics, and there was a
whole list of numbers to be avoided for various reasons, mainly
because the wheel did not revert to the resting position as soon
as it detected a mismatch, as the transistorized selectors did.
It only reverted to rest when the digits from the phone company
transmitter ceased and a mismatch occurred. Thus, if you picked
the wrong number to use, the phone could ring when someone else
was dialed. That must have been very confusing. In other words,
there were some numbers which added up to the same number of
ratchets of the wheel such that the bell would ring. Also, the
number selected couldn't add up to a total larger than a certain
figure. This limited the available number pool.
Regards,
Geoff
^top of page^
The Telephone Name EXchange Project by
Robert Crowe (click here to go there)
IMTS or Improved Mobile Telephone
History Links below:
MOTOROLA EARLY LAND MOBILE EQUIPMENT
INDEX, 1938-1946
http://www.mbay.net/~wb6nvh/Motadata.htm
Geoff is an ardent mobile radio
enthusiast, please visit his site soon.
