parnass@ihu1h.UUCP (Bob Parnass, AJ9S) (06/09/85)
x
George Chao, a cellular phone user, provided this article,
published in the May 1985 'Ameritech Connection' by Ameri-
tech Mobile Communications, Inc. for its Chicago/Gary area
cellular telephone users:
Confidentiality Could Be A Three-Way Street
"One of the differences between cellular service and
conventional mobile telephones is that cellular is
'private-like.' Each side of every cellular conversa-
tion is assigned its own private radio channel by our
computerized system, so there is no operator to go
through and there are no party lines to share."
"However, in the last six months, sophisticated elec-
tronic scanners able to monitor cellular radio frequen-
cies have become available, and Ameritech Mobile cau-
tions you about conversations of a highly confidential
nature held over your mobile telephone."
"Scanners are only able to lock onto one channel at a
time and can not simulate our computerized network. In
fact, they can ONLY detect one side of the cellular
conversation and ONLY for a brief period of time.
That's because our computer routinely switches your
call from one channel to another to keep the transmis-
sion quality of your conversation at a high level as
you drive through the cellular service area."
"While scanners are expensive and not routinely used by
the general public, be careful in discussing
proprietary or very personal issues when using your
mobile telephone. Remember the airwaves are public
property."
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Bob Parnass, Bell Telephone Laboratories - ihnp4!ihu1h!parnass - (312)979-5414rjr@mgweed.UUCP (06/12/85)
One correction to that article on cellular is that you can hear both sides of the conversation on one frequency. There is sidetone in the system and if you monitor the cell xmit frequency, you will hear both sides. Bob K9EUI
jgpo@iham1.UUCP (John, KA9MNK) (06/13/85)
> > One correction to that article on cellular is that you can hear both sides > of the conversation on one frequency. There is sidetone in the system and > if you monitor the cell xmit frequency, you will hear both sides. > > Bob K9EUI Actually, the sidetone is generated in the mobile unit. You might be able to hear the mobile-originated side of the conversation by listening in on the cell site, but that would be due to crosstalk in the switch and would probably be at least 10 dB down. John Opalko Autoplex (TM) 1000 Development Group (the cellular people) AT&T Bell Labs Naperville, IL ...!ihnp4!iham1!jgpo