A couple of CP040 questions

[noleftturn]

Hi All

Greetings from Cape Town, South Africa.

My local neighborhood watch is about to "arm" ourselves with CP040's. We're getting our frequency license from the authorities shortly. We're starting off with about 20 radios but will be getting more and more as the various community members buy into the idea.

We also want to record everything onto a computer. Being a software engineer the recording part isn't going to be too hard, but what I'd like to know is this:

1. What is the audio out connector on the CP040? (You'd think the technical spec would mention it)
2. We've been told by the guys that are selling us the radios (I may have misunderstood) that each radio has an identifier and that the more fancier radios would be able to display the ID of the transmitting radio. Is that correct? Is there any way to record both the audio and somehow a stream of identifiers?
3. Again, second hand information via the salesmen & the shocking downloaded user manual is that we can have psudo channels (private lines) on one frequency? How does this work? (Feel free to point me to a url, I'm not averse to RTFM'ing)
4. Assuming these Private Lines, how many can we have? And can we have a way of broadcasting to all radios in case of an emergency?
5. The most logical application of these private lines would be to allow us to leave a radio on at night (while some people chat) and only be woken up in the event of an emergency.
6. Is there a way to record all of these private lines simultaneously? Any way for the radio to output them on different analog lines?

Thanks a million in advance.

j.

[noleftturn]

Hi

I realize that some of my questions were a little complicated, but if anyone could answer any of the questions it would be most appreciated.

Regards.
j.

[Tom in D.C.]

With regard to only one part of your inquiry, that being the question of "private line" use,
you have been misled by the sales people and terminology used into thinking that the
feature is something that it is not. Here is how it works. You have a single frequency on
which you talk. Added to that frequency can be a subaudible tone. If other radios are
set up to that they only produce audio when the transmission with the subaudible tone is
received then they do not hear other transmissions on the frequency. The system can have
multiple users, using different subaudible tones, so that you and others and don't hear
transmissions they don't want to be bothered with. However, if you press the "monitor"
button on your radio, you can hear ALL of the transmissions on the channel. So, the word
"private" is being misused because nothing about the transmissions is private. Another
factor to be considered, for example if you have Area A using tone 1 and Area B using tone 2,
is that you must use your monitor button to listen before you transmit to be sure no one
else is using the frequency. Use of the words "private" and "privacy" where it concerns
tone coding is, as I said above, a misleading advertising gimmick. The only way to sort of
guarantee that others can't understand your radio transmissions is to use encryption which
is another game completely and usually used only by people with deep pockets, such as
police agencies, etc., and even then only on certain frequencies.

If the object is to have a separate communications path for people such as supervisors you
could possibly get a second radio frequency assigned. Then you give radios with only one
channel to the troops and radios with two channels to the supervisors.

Frequency and channel, by the way, mean the same thing.

If you're going to spend good money for twenty or more radios, perhaps you should be
looking at other units, such as Motorola's digital units, like the DTR2450. There you would
actually gain some privacy and other features that the CP040 can not provide.

Regards,

[noleftturn]

With regard to only one part of your inquiry, that being the question of "private line" use...

Thanks Tom, I really appreciate your reply.

I think I understand the concept of the sub-audible tones now.

Just to clarify:
1. Does one of the knobs on top of the radio specify which tone to use? or to not use a tone?
2. If a radio receives a transmission without a sub-audible tone does that transmission get "played" or ignored?
3. Is there a way on a radio to tell it to not send the sub-audible tone when transmitting? (ie, in case of an emergency to get people who are monitoring any of the tones to hear the message?)

thanks
j.

[Tom in D.C.]

J:

1. The tone is usually programmed into the radio and on radios such as the CP040 there is
no external control. Knobs on top are channel selection and volume, usually.
2. To answer your question I have to dig a little deeper into how tone coding is applied:
A. Tone coding can be used for both receive AND transmit on your radio, or it can be
used on transmit only. Of course the radio can also be set up for no coding at all.
B. Transmit only is called "tone;" whereas transmit and receive is called "tone coded
squelch." These are the customary terms in the USA, and your terms may be
somewhat different but it all works the same.
C. So, if a radio is set up for tone coded squelch it will only pass audio that has the
correct tone. If not it will pass all audio. If a signal with the wrong tone code is
received the radio will remain quiet, and this applies as well to a signal with NO
tone coding on it if your radio is set to received tone coded transmissions only.
3. As far as switching the tone coding on an off, the way it's done with a CP040 and
similar units is with the side "monitor" button. On fancier radios you usually have a toggle
switch that can turn off the receive tone coding for as long as the switch is turned the other
way. On most Motorola radios that are set up to transmit a tone code the radio always
does so. Old Motorola MT500 radios, dating back more than twenty years, had a monitor
switch on top so you could hear everything on the channel, but the radio still would always
transmit the tone code. This has been a pretty universal way of doing things. There are
some much fancier ways of emergency notification, both from the dispatcher to the user
and vice-versa, but these are done with higher grade radios.