tom@syssoft.com (Rodentia) (03/20/91)
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. -- 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 |
lrk@k5qwb.UUCP (Lyn R. Kennedy) (03/22/91)
tom@syssoft.com (Rodentia) writes: > Last night (3-19-91), the news referred to the release of transcripts > from portable terminals the police use for non-voice, inter-unit The one I saw on the news was not 'portable' but 'mobile'. There are such portable terminals but most are mounted in the cars and use power, radios, and antennas mounted in the usual way. > 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? Most of these systems use standard frequencies you can find in the Radio S___ book but some are on odd freqs assigned to some other service. You can hear them but they sound like modems. Each manufacturer has it's own methods, rates, etc. The one I saw on TV looked like the Electrocom Automation version which I've found using two modulation methods. The ECPA may prohibit listening ( watching? ) these systems but I'm not sure. There are systems in use by businesses, most notably Federal Express and IBM (855.8625?). The news didn't say so, but I suspect the system has a log built in and the transcript probably came from the main computers which run the system. The mobile terminals are operated by a smaller computer which makes them look like ordinary remote terminals used by many computer systems. > > Thanks in advance. > -- > Thomas Roden | tom@syssoft.com --------- lrk@k5qwb.UUCP lrk%k5qwb@kf5iw.UUCP 73, utacfd.utarl.edu!letni!rwsys!kf5iw!k5qwb!lrk Lyn Kennedy K5QWB @ N5LDD.#NTX.TX.US P.O. Box 5133, Ovilla, TX, USA 75154 -------- "We have met the enemy and they are us." Pogo -----------------
dave@seas.gwu.edu (David M. Owczarek) (03/23/91)
In article <1991Mar19.172627.22156@syssoft.com > tom@syssoft.com (Rodentia) writes: >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? I don't know any of the technical details, but I believe there are similar units commercially available. For example, taxicabs in Arlington, VA use a non-voice terminal which is pretty powerfull. It can locate all cabs to fairly specific areas, pass messages, etc. I would assume that police units have frequencies that are restricted, at least for transmission. And I bet the LAPD would prefer not to have you listening in on them :-). >Thanks in advance. >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 | -- ---------------------------------------------------------------------------- Dave Owczarek, Operations Team dave@seas.gwu.edu or uunet!seas.gwu.edu!dave The George Washington University Engineering Computing Facility, Wash. D.C. ----------------------------------------------------------------------------
onymouse@netcom.COM (John Debert) (03/24/91)
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