I am not quite a newbie... but my experience with scanners falls short with my new situation.
I have recently moved to Wareham Mass.The Police, Fire and other local frequencies also use a tone...
I know nothing about tones or why they are used... I have a Pro-95 handheld scanner and am under the impression that it is no longer any use to me now that I am trying to listen to a town that uses a tone...
Can someone please explain to me what type of scanner I will need to buy (and maybe a little explanation of tone...
Thanks
You weren't specific as to the "tone" question but in general, for radio use, when tones are used they are used for a form of selective signalling. The idea is to make the use of one frequency for multiple different users possible by making each radio only unmute for the desired users/agency and not for anybody else or any random static or interference.
Usually, when tones are discussed it involves the use of CTCSS or DCS tones which are broadcast continuously along with the transmissions. This is also called "tone squelch". A properly equipped radio will only let sounds out of its speaker ("unmute") when the transmission being received matches a pre-programmed tone setting. So, say County A fire department uses a frequency for its dispatch but it shares that frequency with a city in a neighboring county's ("County B") city FD located far enough away so that simultaneous transmissions won't really cause problems for each other but close enough that they would cause confusion if each department had to hear each others' traffic. Using different CTCSS (or DCS) tones would alleviate this issue - County A radios would only hear County A radio traffic and be silent when the city FD radios in County B transmit. You'll often see CTCSS referred to as "PL" and DCS referred to "DPL" as well - the PL and DPL terms are really Motorola proprietary names but, like Xerox in terms of paper copiers, the terms have become nearly generically used. The real generic terms that SHOULD be used are CTCSS = Continuous Tone Controlled Squelch System; and DCS = Digitally Controlled Squelch. Motorola's PL stands for "Private Line" (though it is not really "private") and DPL stands for "Digital Private Line". CTCSS uses a continuous subaudible tone (supposed to be below audible frequency range but some can be heard depending on the radio's audio filters and the listening individual's hearing ability) while DCS use digital pulses sent continuously at a rate that is, again, supposed to be subaudible. In both cases they are only used for analog FM transmissions; digital signals like P25 have their own selective signalling capability which are inherent in their overhead data stream. This is also primarily for conventional systems - trunked systems use different techniques but some analog trunked systems can use forms of tone squelch but in a more complex way than the conventional model I just described.
There is also two-tone selective signalling usually used for fire dispatch systems such that the dispatch transmitters send a special alerting set of tones that are usually used to activate a receiver in a fire station when needed to alert the personnel at the station but keep the receiver muted otherwise. Those types of tones are in the audible range and can easily be heard.
In either case, the added effect of using tones is that any undesired traffic is not heard whether it is co-channel users or static or interference.
If your receiver can use tones and you know which ones to program (if known, they are usually provided in RR's database along with the radio frequencies) then they can be useful in blocking out undesired co-channel users as well as any interference (the interference is still there, of course, but you just don't hear it, at least when no signal with the correct tone is present).
If you have a frequency programmed in with no tone or have a receiver that has no tone squelch capability then you will simply hear all traffic on that frequency; if the frequency has only one user group on it within your range of reception then you won't have any problems but if there are other users that are also on that frequency within range of your receiver then you will hear them also, whether or not you want to, of course.
-Mike
