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From: mark@drd.UUCP (Mark Lawrence)
Newsgroups: comp.dcom.modems,comp.mail.uucp
Subject: Re: RF modems
Keywords: radio data communications
Message-ID: <289@drd.UUCP>
Date: 11 Oct 88 12:59:58 GMT
Article-I.D.: drd.289
References: <183@arnold.UUCP> <1988Sep20.184054.2403@utzoo.uucp> <184@arnold.UUCP> <1988Oct5.232838.15239@utzoo.uucp> <1276@nesac2.UUCP>
Reply-To: mark@drd.UUCP (Mark Lawrence)
Organization: in *this* company!?
Lines: 43

%%  In article <379@chief.UUCP> lance@chief.UUCP (system administrator) writes:
%%   ... Where can I find information on RF modems?

I posted a similiar query earlier and have since discovered a company
that does something like this.  The company is DataRadio, Inc. with offices in
Montreal (1819 Dorchester Blvd W., Suite 400, H3H 2P5) and Atlanta (400
Perimeter Center Terrace, Suite 730, 30346).  They sell a modem that 
will connect up to a radio that will transfer data at 4800 bps.  They 
claim that it is x.3 and x.29 compliant.  The device is called a Modem 
Data Link Controller.  I quote from the marketing brochure:

Features
.	adds data to your existing fixed or mobile radio system
.	up to 4800 bits per second
.	Collision Avoidance Radio Multiple Access (CARMA) protocol
.	uses external VHF, UHF radio transceiver
.	shares channel with voice using an efficient carrier detection circuit
.	forward error correction for mobile environment
.	RS-232 interface at 50-9600 baud with buffering & flow control
.	separate digital I/O port for telemetry and alarms
.	built-in user controlled data privacy
.	available with built-in 5 port mux

Very interesting item of note: these things are addressable; you can
have up to 255 modems in an RF network.  It does encryption using a 128
bit key but don't know if that's available on the version sold in
Canada.  The vendor uses crosstalk on their demo setups (Does anybody
know whether crosstalk requires a full duplex circuit?)

Henry expressed concern about the legalities of slinging data about on 
channels licensed for voice.  I haven't called up the office in Toronto 
and asked specifically, however, I assume since the company is selling 
the things in Canada, they must be meeting the Canadian equivalent of 
the FCC's requirements (and it doesn't monopolize the channel for data).
Price is US$1800.

I don't have any financial stake in these people -- just passing along what I
know.
	
	Mark
-- 
   [uunet!apctrc,romed,tulsun]!drd!mark    DRD Corporation    Pithy Quote
    mlawrence@jarsun1.ZONE1.COM            (918)743-3013      Jer. 9:23,24