Andres Tarzia wrote:
>
> Hi all!
>
> I am designing a PIC-based alarm system. The instrusion detection is easy.
> The local alarm is very easy too.
>
> But I'd like to include some form of remote alarm. I was thinking about a
> regular pager as the alarm receiver, but I don't know how to transmit data
> to it. Does anybody knows how to send an alert to a pager? Please, without
> using the phone. I mean a Pager Transmitter like the one that carrier
> companies have, only smaller.

Given that you want the same range as the commercial paging towers, you aren't
going to have a transmitter that is much smaller.  You'll either need to
transmit at a VERY high power, or build a very tall tower.

>Provided that one can build/adquire the
> equipement, is it legal?

It sounds like you are not in the US, so you'd need to check with your country's
equivilant to the FCC.

>Does the FCC allows you to transmit in the Pager
> frequencies? Or are they restricted? Do you need some kind of licence?

Generally, yes.

>From your other messages, it sounds like you want to distribute your
transmitters according to your needs.

The upshot is that it is not an easy nor an inexpensive thing to do.  You can
certianly add extra circuitry to your current pager... but chances are that
unless you are *very* good at radio receiver design, you aren't going to fit
your own circuit in there, nor will you draw as little power as theirs.

Secondly, if you want a range that's larger than 1/2 km, you're going to end up
with transmitters that must be licensed (unless you live out in the boonies)
And I'm guessing that if you want an alarm for your car, you live in a
metropolitan area where car-jacking is not uncommon.

It would be easier (and cheaper) to get a cheap cell phone for your car, and
each location where you need it, hook it up to a simple dtmf circuit which would
then page you through the phone system.  I don't know where you are, but here we
can get a cheap analog cell phone for nothing, and about $5-$10/month for
service.  Find an unscrupulous phone dealer who'll sell you 3-5 phones and put
them on the same service (ie, you can dial out with them, but don't plan on
receiving calls with them) and you should be all set.

Yes, it's more complex than the system you would like to build, but pager
transmitters and frequency allocations are not inexpensive.  If you have wads of
money to blow on that sort of thing, knock yourself out, but if it were myself,
I'd look at other options.

-Adam