Date: Tue, 28 Jul 1992 03:30:53 GMT
From: wtm@uhura.neoucom.edu (Bill Mayhew)
Newsgroups: comp.dcom.telecom
Subject: Re: Should I Keep My Cellphone Off When Not Using it?
Organization: Northeastern Ohio Universities College of Medicine
X-Submissions-To: telecom@eecs.nwu.edu
X-Administrivia-To: telecom-request@eecs.nwu.edu
X-Telecom-Digest: Volume 12, Issue 594, Message 3 of 9

I've noticed that my Uniden cell phone sends out some sort of inquiry
a few seconds after being swtiched on.  That inquiry is something in
addition to sensing of SERVICE AVAILABLE condition.  Detaching the
antenna makes the SERVICE indicator turn off immediately.  Reattaching
the antenna makes the SERVICE indicator turn on immediately.

I have Cellular One as a carrier.  In this area, Celluar One is an A
service "wireline" system, I believe.  The system seems to keep track
of the last location of mobile sets until midnight of the current day.
For instance, if you have automatic follow roaming turned on, it is
cancelled each midnight.  Ringing seems to go out to all cells in the
last known serice area of the unit, as it is perfectly possible that
the unit might have crossed cell boundaries since the last contact
with the unit.

You are correct that the mobile unit does periodically talk to the
system.  My unit makes some sore of inquiry every five minutes while
it is switched on.

The sytem doesn't waste too much bandwidth attempting to contact a
mobile unit.  When I dial my switched-off cellular phone, the system
will generate approximately four ring-back tones before it switches
over to an intercept recording saying, "The Cellular One phone you are
calling is either switched off or out of the area."

I'm not sure what the period inquiry is doing.  The manual says that
the phone will try to re-establish service every five minutes.
Apparently, the phone expects to get an answerback from the system in
addition to sufficient signal quality.  If the phone has gotten an
answerback from the a correct A or B system and signal level is
maintained, it must presume it is still in the service area.  The
uniden phone I have also automatically adjusts its transmitter power
between a few mW and three watts depending on the strength of the
signal coming from the cell.  The results of this can be interesting
in marginal conditions because the phone will go to a full three watts
when it can't hear the cell in the middle of a call.  The cell,
apparently having a much better reciever continues to hear the phone.
I've had a number of calls where I can not hear the person I'm
calling, but the person can hear me.

All in all, I'd switch off the phone when you don't need it.  This
will keep you from getting junk calls and wrong numbers.  The system
probably has to ring all the cells, or least some number, starting in
your last known position anyway.

As a side issue, I've noticed that my cellular phone has yet to
receive any sort of junk telemarketing call.  I presume that cellular
prefixes must be some magic taboo for telemarketers -- or it could be
that since most cellular users switch off phones while out of the car,
etc., that the hit rate is low enough that sequentially calling in
cellular prefixes is a waste of time.

My pager, on the other hand, recieves a lot of wrong numbers.  My
number xxx-5225, must be close to that of some local drug dealer.  I
get a lot of xxx-xxxx-911 displays on my pager.  Usually about
23:00-00:00.  The prefix is often in the downtown area.  I've
occasionally called those numbers out of curiosity.  They've all been
older women with noticable ethnic accent ... or they might be old
ladies trolling pagers just to get a human with which to talk; naah.


Bill Mayhew NEOUCOM Computer Services Department Rootstown, OH
44272-9995 USA phone: 216-325-2511 wtm@uhura.neoucom.edu (140.220.1.1)