I'm not sure about POCSAG but I understand that in order for the pager
receiver to last so long on a 1.5V battery is that it knows when to listen
for a page and when to shut off.  Reduced current draw extents battery life
of course.

If you are not on a network that provides a sync signal then your pager will
cycle on/off looking for the signal.  That don't mean that it will not work
as you want, you may just have to live with reduced battery life or transmit
a sync signal during idle times from the transmit location.

I am pretty sure this is how the FLEX type pagers work.  In a few years all
pager networks will be using the FLEX protocol.

So, look at Motorola web site or do a web search on FLEX also.

Paul




In a message dated 99-09-03 08:18:38 EDT, you write:

<< Hi Mike,

 Thanks!
 I'll start searching the web for POCSAG.

 By the way, I'm not based in the USA, but in Argentina.

 I understand that I will not have access to commercial frequencies, but I
 was thinking on "modifying" a standard pager to receive on a custom
 frequency. The question is: which frequency? And supposing I can find a
 "free" range, will I need FCC (or our local equivalent) clearance? Will I
 need a license?

 I'd like to cover at least 50 Km (that is a little over 30 miles), so I will
 need a fairly powerful transmitter...

 Look, I could build a custom receiver and let pagers alone, but I will never
 build such a good-looking, small, lightweight, low-power unit like the
 commercial pagers. Using PICs and standard LCDs, I will end up with a big,
 ugly, heavy case, 3 standard battery cells or a custom battery, lasting just
 a few days, etc. Standard pagers use custom VLSI chips, and custom LCDs and
 use just a single AAA battery cell, that lasts for over 20 days.

 Again, thank you for your help.

 Regards,
 Andres Tarzia
 Technology Consultant, SMART S.A.
 e-mail: atarzia@smart.com.ar


 -----Original Message-----
 From: Mike Cornelius [mailto:mike@BYTETHIS.COM.AU]
 Sent: Thursday, September 02, 1999 23:57
 To: PICLIST@MITVMA.MIT.EDU
 Subject: Re: [OT] Pager Transmitter


 Hi Andres,

 This is actually quite simple, the standard paging protocol is known as
 POCSAG, do a web search and you should be able to find details.
 Basicly paging transmissions consist of a preamble (512 alternating bits
 from memory) followed by a number of codewords which consists of 21 bits of
 data followed by 11 bits of CRC (This may not be exactly right as it's been
 4 years since I looked at the protocol).
 Actual RF transmision is simple FM FSK. A 1 is FC +4.6Khz A 0 is FC -
 4.5Khz.

 The encoding side of things for your app could be done with a 12C508, I can
 help you with code if you like, although I don't actually have code for
 POCSAG specificly but I do have something very similar (in fact it would
 have been POCSAG but I needed more bits per codeword).

 The transmission side is pretty easy too, there are plenty of rf modules out
 there you could use or build your own.

 In terms of licence regs I'm not sure about regs in the USA but in Australia
 there are a number of options depending on whether you need in house or wide
 area coverage. Naturally enough though you won't be able to use the same
 freq as an existing wide are provider.

 Regards, >>