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From: onymouse@netcom.COM (John Debert)
Newsgroups: sci.electronics
Subject: Re: Police Teletypes - Can one scan for them?
Message-ID: <1991Mar24.055948.11573@netcom.COM>
Date: 24 Mar 91 05:59:48 GMT
References: <1991Mar19.172627.22156@syssoft.com>
Organization: Netcom - Online Communication Services  UNIX System {408 241-9760 guest}
Lines: 33

From article <1991Mar19.172627.22156@syssoft.com>, by tom@syssoft.com (Rodentia):
> Last night (3-19-91), the news referred to the release of transcripts
> from portable terminals the police use for non-voice, inter-unit 
> communications.  Does anyone know the frequencies, modulation methods, 
> baud rates, etc.?  Would it be legal to scan for these the way civil
> voice bands are scanned?  Is there a commercial version of these?
> 
> Thanks in advance.
Many (esp. large metro area) police departments use data terminals in their 
vehicles to reduce the need for voice traffic. These are made by Motorola,
General Electric and others. These kinds of terminals are also available for
commercial use. They use the same radios, perhaps only slightly modified, as
are used for voice communications. The police data terminals operate on
frequencies assigned for police use or on local government freqs, depending
on what the agency has available and decides to assign. It is said that the
data is encrypted but I have found no evidence of that. The technology used
ranges from common slow Baudot (<=45cps) to Bell 202 (120cps) to the data
transmission methods used in cellular phones (~1Kcps+). 

I don't have info on what freqs are used by LAPD for data but check all their
police and local gernment freqs-you'll be able to easily recognize data
signals. Also take a look at LA County freqs, including their trunked system
from 866 to 868.8MHz.


> -- 
> Thomas Roden                                      | tom@syssoft.com
> Systems and Software, Inc.                        | Voice: (714) 833-1700 x454 
> "If the Beagle had sailed here, Darwin would have | FAX:   (714) 833-1900
> come up with a different theory altogether." - me |
-- 
jd
onymouse@netcom.COM