Post by thread:[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, ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Mike Cornelius Internet: .....mikeKILLspam@spam@bytethis.com.au Byte This Interactive Phone: +61 2 9310-2157 PO Box 1342 Strawberry Hills FAX: +61 2 9319-3948 NSW 2012 Australia URL: http://www.bytethis.com.au ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > {Original Message removed}

Hi, Here is a snippet from something I saw a while back. I have the files I can send you. It appears that the URL link is dead. However the email address might be good. I think I have the source code somewhere. ++++++++++++++++++++++++++++++++++++++++++++++++Description: This project describes a basic pocsag encoder system utilizing a microchip 16C84 micro controller. The system is specifically designed to encode multiple pre-programmed numeric messages to pocsag compatible pagers. An external rf-transmitter section is required for this function, and that rf section is deliberately omitted from this documentation (you are on your own). Disclaimer: This source code is provided on an 'as is' basis for educational purposes only. No guarantee is provide or implied for any implementation or purpose. I do not assume any liability for any business loss, property loss, personal loss, personal injury, or any other kind of loss (I don't want to hear about your dog). Use at your own risk! And specifically do not use for any life support or other safety related purpose. SO THERE! Copyright: Poc_code.asm is copyright Henry Carl Ott (that's me). You are free to use it in non-commercial applications. Any commercial or for profit use requires specific permission from me. Credits: Basically the inspiration for the project came from the rx pager design by Dejan Kaljevic. His code does pocsag decoding. If you want to learn about pocsag decoding, take a look at: http://www.geocities.com/SiliconValley/Horizon/6063/) Unfortunately pocsag encoding requires an entirely different approach so I had do just about everything from scratch. Most of the subroutines are modified microchip app notes, but I also got a lot of great tips and ideas from the pic microcontroller discussion list. Too many to mention individually, a really great bunch of guys. Look to: http://www.myke.com/piclist/ for a good faq and subscribe instructions for the list. All of the truly awful code in the design is mine alone. NOTE: If you need to know the specifics of the pocsag protocol, this is not the place. I suggest you do some additional searching on the web. Operation: The source code is written to assemble under MPLAB, it may require minor modification to assemble properly in other design environments. The hardware consists only of the pic, a 3.6864 crystal, and the rs-232 interface. See the included schematic for pin assignments. The program has two basic modes of operation. 1. The stand alone encode mode. When you press a button a pocsag message is generated. 2. The program mode. While connected to a dumb terminal the cap code and other pager specific information is pre programmed in to 16c84's eeprom. The buttons do nothing. Programming: The 16c84 has 64 bytes of eeprom. This memory is used to store 4 paging 'profiles'. Each profile contains all the information to generate a single pager message. The profile contains: the pager cap code (or pin), the message function (0,1,2,3), the message baud rate (512,1200,2400), a flag to determine if the output data should be inverted, and an optional numeric message (at the moment 5 digits max). So here we go: Hook up the completed unit to any rs-232 terminal (or program) configured 9600 8N1. Hit any key and you should get a '.' prompt. At this point you can hit 'x' (case does count) to exit back into the encode mode, or hit 'p' to program a specific profile. If you don't hit anything the program will exit back into the encode mode on it's own after about 20 seconds. If you are in the program mode you will be asked to enter the profile data. PROFILE= ; select a specific pager profile to update 0 - 3 (no error checking here) CAP= ; a valid 7 digit decimal cap code (no error checking) FUNC= ; the page function bits 0-3 BAUD= ; the baud rate to transmit 0=512 1=1200 2=2400 INV= ; 0=normal output data, 1= inverted output data MSG? Y/N ; if this profile contains a numeric message. If no, a tone only page will be generated. ; if yes, you will be prompted to enter a 5 digit message. spaces an d '-' are supported. If you make a mistake or wish to cancel hit a non valid key and you will get another '.' prompt and will have to start over. NOTE that if you screw up in the middle of a profile, that whole profile will me marked invalid. But the other profiles will be left untouched. You can configure four completely different profiles to activate 4 different pagers, or send four different messages to the same pager. Encoding: After you exit the programming mode, or if you are in the default mode at power up, pressing one of the buttons will generate a pocsag message for the profile that is associated with that button. The PTT line is asserted to key up a connected rf transmitter. after a .25 second delay (approx) the encoded batch data is shipped out the poc_data pin. The PTT line is de asserted Note that in this prototype no input conditioning is attempted (debounce). The intent is that you can re-write the main routine to handle any sort of input device. That's all folks. There's plenty of room for improvement, if you add on any gee wiz functions or find any bugs please be sure to drop me a line. Have fun, and if you have any questions send me some mail at: carlottKILLspaminterport.net PCS Engineering Norman Gillaspie 325M Sharon Park Dr. #210 Menlo park, Ca. 94025 Tel 650-854-5263 Fax 650-854-5445 KF6WHG Email .....normanKILLspam.....pcseng.com > {Original Message removed}

Anne Ogborn wrote: > >It's >a) impractically complex. Figure on hiring a couple people. > >b) a pager frequency license was recently sold for the SF bay area for 22 million, >if memory serves. > >What's your objection to using the phone lines? Simple enough to get a pager & activate >it, then don't give anybody the number. Make a circuit (or use the modem if you've >got a PC in the system) to dial the pager number, and off it goes! > >Indeed, if it's an alphanumeric pager, they're usually connected to email addresses. >Make your software email your pager when the alarm trips. >Check the latency in this, but it's usually trivial compared to the pager latency anyway. > > >-- >Anniepoo >Need loco motors? >http://www.idiom.com/~anniepoo/depot/motors.html > The problem is that I'd like to use a modified version of the alarm for my car, with a different message going to the SAME pager. Eventually, I could have a bunch of autonomous systems paging me if something goes wrong... Get the idea? Thank you for your help! Regards, Andres Tarzia Tecnology Consultant, SMART S.A. e-mail: EraseMEatarziaspam_OUTTakeThisOuTsmart.com.ar

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: atarziaspam_OUTsmart.com.ar {Original Message removed}

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: @spam@atarziaKILLspamsmart.com.ar {Original Message removed}

In a message dated 9/3/99 8:28:37 AM Eastern Daylight Time, KILLspamPDRUNENKILLspamAOL.COM writes: > 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 One of the postings to this thread mentioned having a PIC send an email to the pager, (I think). My question is: Is there an ISP that one could subscribe to that you could just have a PIC dial into and, when the phone is answered, send a *canned* email to a text pager? Thanks, Max

That is true but: a) pagers turn on/off the recieving circuit and logic is always on. b) When a message is going to be transmitted the POCSAG protocol start with a "preamble signal" repetions of 1 & 0, at least 576 bits. This makes a pagers wake up (turns on reciving circuit permanly) and listen to the syncronization & rest of the batches. pager will return to the battery-save-cycle if the CODE ID is not his or after recivieng the message. About FLEX protcol, forget it is to complex and motorola will not give FREE this kind of information. Regards Juan Jimenez. ______________________________ Reply Separator _________________________________ Subject: Re: [OT] Pager Transmitter Author: RemoveMEPDRUNENTakeThisOuTAOL.COM at smtplink-dl Date: 03-9-99 8:26 AM 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.

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

>I'd like to cover at least 50 Km (that is a little over 30 miles), so I will >need a fairly powerful transmitter... > >Andres Tarzia >Technology Consultant, SMART S.A. >e-mail: RemoveMEatarziaTakeThisOuTsmart.com.ar > That is going to be a problem. Most commercial pagers work on a cellular basis: various transmitters transmit the message at the same time from various locations. These fairly strong transmitters are locarted on high buildings or hilltops to improve coverage. If you want to have good coverage indoors and outdoors in an area with a radius of 50 km you are roughly looking at a vhf transmitter of 40 W or more with an antenna at a hight of 25 - 30 meters (very roughly) in flat country. Exact fieldstrenght calculations would be necessary. Also depends on the transmitting frequency: the higher the frequency the more power you need for indoor reception. The values given are based on the 144-1448 Mc amateur frequencies and experience with amateur repeater stations. In mountainous country it would be impossible to do without one or more repeater stations. Henk Tobbe - VK2GWK(PA0ADC)

If you are located in the US, take a peek at the Motorola website and search for CreateLink2XT. It's a 2-way pager module that will allow you to originate pages to other pagers on the Skytel system or send email. Single unit cost is about $140 or so, and service from Skytel is dependent on how many bits you push through. Disclaimer-I am one of the design engineers that worked on the product, but I don't get a cut from Motorola. Dave Bengtson On Thu, 2 Sep 1999 14:09:26 -0700, in you wrote: {Quote hidden}>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. Provided that one can build/adquire the >> equipement, is it legal? Does the FCC allows you to transmit in the Pager >> frequencies? Or are they restricted? Do you need some kind of licence? > >It's >a) impractically complex. Figure on hiring a couple people. > >b) a pager frequency license was recently sold for the SF bay area for 22 million, >if memory serves. > >What's your objection to using the phone lines? Simple enough to get a pager & activate >it, then don't give anybody the number. Make a circuit (or use the modem if you've >got a PC in the system) to dial the pager number, and off it goes! > >Indeed, if it's an alphanumeric pager, they're usually connected to email addresses. >Make your software email your pager when the alarm trips. >Check the latency in this, but it's usually trivial compared to the pager latency anyway.

<x-flowed> As other people have mentioned, stay away from FLEX. It's way more work then necessary. Pocsag should be able to do what you want. The code for a 16c84 based pocsag encoder is available here: www.users.interport.net/~carlott/projects.html The code is some early stuff of mine and some of the routines are downright terrible. But it does work! Encoding pocsage is not that tough, you just have to keep the timing tight. I'm in the process of re-writing the code to streamline a bit and add some additional features. It would still be a good place to start. In my project I deliberately left out details on the rf end of things. Here however are a couple of things to investigate. This is all very United States oriented, mileage may vary in your country of interest. Don't even bother to try to tranmit on existing pager frequencies. There are sources available to re-crystal a pager onto other more useful frequencies. Just try to make get those frequencies close to the original pager receiver freq so that the pager's RF front end won't loose too much sensitivity. Re-crystal a cheap 900 mhz pocsag pager onto the low power 915/916mhz control band (US freq./ actual freq. may vary for your country). Then use a RFM/lynx/dvp/whatever low power transmitter on the same freq. I'm not sure which of these x-mitters are capable of sending the direct fsk you need to modulate the signal, time to do a little research. Or, if you are a licensed ham radio operator you could re-crystal the pager onto one of many amateur frequencies. You could then transmit with some real power, but you would also have to add into the transmission some voice or morse code to identify the transmitting station (not a big deal), people are doing this all the time.Note that this is not an acceptable commercial solution. Depending on the area you are in you could get a business band radio license and re-crystal for that. It's not that hard to get a low power license (<2watts in the uhf band). There are less restriction on what you can transmit in the business band then there are on the amateur frequencies. Back on the ham subject, you also may want to look at the following website; http://www.kantronics.com The have a packet TNC that also does pocsag (kpc-9612), along with some dedicated paging encoders. Hope these rambling were of help.... But trust me about the FLEX. At 11:12 AM 9/1/1999, you wrote: {Quote hidden}>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. Provided that one can build/adquire the >equipement, is it legal? Does the FCC allows you to transmit in the Pager >frequencies? Or are they restricted? Do you need some kind of licence? carl -------------------------------------------------------- Henry Carl Ott N2RVQ carlottEraseME.....interport.net http://www.interport.net/~carlott/ -------------------------------------------------------- You're entitled to your own opinions. You are not entitled to your own facts. </x-flowed>