hardie@sask.UUCP (Peter Hardie) (10/15/84)
Can someone please enlighten me as to what the three abbreviations stand for. And what is the difference in function between the three. One (DTMF) is the touchtone frequencies, but I am not sure of the other two. MAIL replies to me at IHNP4!SASK!HARDIE and I'll summarize if I am not the only ham who doesn't know! Tnx + 73 Pete ve5bel
jim@infoswx.UUCP (10/17/84)
Pete -- Here's a brief explanation of PL and CTCSS. First of all, they are one in the same. CTCSS stands for 'Continuous Tone Coded Squelch System'. PL stands for 'Private Line' and is a registered trademark of Motorola, Inc. Another name commonly used is 'Channel Guard' which is a General Electric trademark. Now for the technical details (I'll use the term PL 'cause it's short!) -- Basically PL is nothing more than a sub-audible, low amplitude tone that is transmitted along with the normal speech audio. When heard by a receiver that is equipped with a PL decoder, the sub-audible tone will be detected and the receivers' audio output stage will be activated. If the transmitted signal does not contain the proper PL tone (there are 37 of them), the receiver squelch won't open, hence no audio thruogh the speaker. This scheme is primarily used by commercial two-way and public service radio services, and in fact is required by the FCC in those applications. PL is in use by amateurs in the US to a small degree, mostly on repeaters in the 440- 450 MHz band to alleviate intermodulation problems. In commercial applications another advantage is that a large number of users, i.e., Joe's Plumbing, Speedy Courier, and Pink & Green Taxicab, can all share the same frequency (repeater) with each using a different PL tone. With this scheme, Joe's base station and his fleet of plumbing trucks will only hear calls from each other and not be bothered by the other users of the repeater. There are some details of actual operation that I have not gone into here, but they are not really necessary in this basic outline. Hope this has helped. 73's, Jim Gerke, KC5OA Infoswitch Corp. Richardson, TX allegra!convex!infoswx!jim
wn9nbt@ecn-ee.UUCP (10/18/84)
CTCSS - Continous Tone Coded Squelch System
DTMF - Dual Tone Multiple Frequency (touch tones, telephone-like)
PL - Private Line (Motorola's name for CTCSS)
Note - CTCSS for General Electric is called "CG" or Channel Guard
and RCA calls it "QC" or Quiet Channel. All the same thing.
.....Dave Chasey -- wn9nbt