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Cellular Phone Forum / General / GSM / August 2004Using standard handset as terminal device
Hi, folks-- I'd like to set up one of our servers here to monitor our computer networks and send short text messages to one or more of our techs' cell phones in case of problems. Seems like the "right" way to do this is with a terminal module-- I was recommended the Siemens MC35i, but this is Telcel land (Mexico) where I can pick up a basic GSM handset pretty easily, but they don't have a clue about dedicated terminal devices. Handset models I'm looking at are Siemens A56 and A55, and Nokia 1100,3100,3595,6100; anybody know whether it is feasible to hook one of these up via RS232 to a computer and control it to send text messages? Also, if I get a handset to play with and manage to obtain a terminal module, can I just put the SIM card from the handset into it and have it assume the personality of that phone? Sorry about my ignorance on how these things work, I'm new to the GSM world... Thanks-- Larry Centro de Investigaciones Biologicas del Noroeste, La Paz, Mexico Any handset would work, as long as it's got a built-in modem module. Most of older GSM handsets do, many newer models don't. Check the phoine's manual to find out. You would be better off using a USB cable if it's a Windows computer. Find the variety that charges the handset's battery. On a Comport cable you may have to do some soldering to connect the charger. Modules are better for high-volume traffic, otherwise the handset's just fine. Yes you can place the simcard into a module or another handset and it would work, provided that the new device isn't locked to a carrier other than yours > Hi, folks-- > [quoted text clipped - 16 lines] > Centro de Investigaciones Biologicas del Noroeste, > La Paz, Mexico > Any handset would work, as long as it's got a built-in modem module. > Most of older GSM handsets do, many newer models don't. Check the > phoine's manual to find out. Thanks. I'm confused. Is a modem used for SMS messages? I thought that was some digital protocal between the phones. Or is it that the modem is required for the PC to phone communications? > You would be better off using a USB cable if it's a Windows computer. Nah, we work in Unix here for the server side stuff. Good point on the battery and charging issues, hadn't considered that. > Yes you can place the simcard into a module or another handset and it > would work, provided that the new device isn't locked to a carrier > other than yours Good news, thanks! --Larry > Thanks. I'm confused. Is a modem used for SMS messages? I > thought that was some digital protocal between the phones. > Or is it that the modem is required for the PC to phone > communications? "Modem" is something of a misnomer in the context of a GSM device. It's more like a general purpose command interpreter for the "AT+C" cellular extensions to the standard "AT" command set. Usual functions include establishing data calls (ISDN or "analog"), messaging (2-way SMS and the reception of cell broadcasts), and perhaps GPRS connectivity. John John Henderson <jhenRemoveThis@talk21.com> wrote in news:2nsr69F42eq1U1@uni- berlin.de: >> Thanks. I'm confused. Is a modem used for SMS messages? I >> thought that was some digital protocal between the phones. [quoted text clipped - 5 lines] > for the "AT+C" cellular extensions to the standard "AT" command > set. Ah, very clear-- thanks. Is that a standard command set for the extensions? --Larry > Ah, very clear-- thanks. Is that a standard command set for > the extensions? In general - yes. Implementations of AT+C commands are standard across manufacturers, but I need to qualify that immediately. Many individual commands are optional, or mandatory only if certain other optional commands are implemented. And the spec for some commands gets interpreted slightly differently by different manufacturers occasionally. An example might be where a null value for a parameter means "all possible values" to one manufacturer, and "no values" (disable the feature) to another. GSM 07.07 has a very useful section on the syntax of AT+C commands, and details the means by which you can query the device's implementation, and permissible range of values. Manufactures often add their own proprietary commands, using a different command prefix. Siemens-specific commands begin "AT^S" instead of "AT+C". John And a little-known fact: many GSM networks block text messages cycling to the same number. You may not be able to send more than 10 to 12 messages in a row to the same number. It the spacing between messages is 10 to 20 minutes, or you use several receipient numbers it would work just fine. > Hi, folks-- > [quoted text clipped - 16 lines] > Centro de Investigaciones Biologicas del Noroeste, > La Paz, Mexico > And a little-known fact: many GSM networks block text messages cycling > to the same number. You may not be able to send more than 10 to 12 > messages in a row to the same number. It the spacing between messages > is 10 to 20 minutes, or you use several receipient numbers it would > work just fine. Sounds like a useful mechanism to prevent abuse, but I kinda doubt Telcel is that enlightened. :> --Larry > Hi, folks-- > [quoted text clipped - 10 lines] > hook one of these up via RS232 to a computer and control it to > send text messages? I don't know about those particular Nokias or the Siemens A56, but the A55 doesn't have an inbuilt "modem" capable of sending SMSs via the serial port. However, an A55 can be firmware-upgraded to a C55 (which does have the modem) using a procedure sometimes described on newsgroups. The cheapest handsets tend not to have inbuilt modems. You should also note that there are 2 common modes for the interaction between GSM device and computer when messaging over a serial connection: text-mode and PDU-mode. Text-mode allows you to send clear text across the serial connection, whereas PDU-mode requires encoding/decoding at the PC end. "hello" in text-mode is "E8329BFD06" in PDU-mode, so you'd need to incorporate the conversion algorithms in your software for a PDU-mode device. Text-mode GSM devices do the conversion internally. Siemens handsets are PDU-mode-only devices, but their terminals support both modes. Ashot's point about providing power may be an important factor in favour of using a terminal instead of a handset. Depending on the fine details of the charge-termination algorithm, a handset battery on constant charge may have a very short life indeed. > Also, if I get a handset to play with and manage to obtain a > terminal module, can I just put the SIM card from the handset > into it and have it > assume the personality of that phone? Sorry about my > ignorance on how these things work, I'm new to the GSM > world... In that direction, yes, but a locked handset may not accept another SIM. John John Henderson <jhenRemoveThis@talk21.com> wrote in news:2ni9qmF182s2U1@uni- berlin.de: > You should also note that there are 2 common modes for the > interaction between GSM device and computer when messaging over [quoted text clipped - 5 lines] > you'd need to incorporate the conversion algorithms in your > software for a PDU-mode device. Good to know, but no problem as long as we have the specs. > Siemens handsets are PDU-mode-only devices, but their terminals > support both modes. Thanks. After reading y'alls comments I'm even more convinced that a terminal is the way to go, but have a bit of a supply problem here in Mexico. Anybody know of dealers for (preferably) Siemens terminals in the southern U.S.A. or Mexico? >> Also, if I get a handset to play with and manage to obtain a >> terminal module, can I just put the SIM card from the handset [quoted text clipped - 4 lines] > In that direction, yes, but a locked handset may not accept > another SIM. Not much worried about that. The packages that Telcel sells pretty much give away the handset and I'd just consider it a disposable carrier for the SIM which would be destined for the terminal module. :> Now the question is where to get a terminal module here in the Americas. Seems like Siemens has much better represantation the other side of the pond... Thanks-- Larry > ... no problem as long as we have the specs. They are available as PDF files (download free after registering) from www.etsi.org. I'd suggest starting with GSM specs 07.07, 07.05, 03.38 and 03.40. Go to the download area (Services & Products), search for each by number, and download a recent version from the unsorted list. > Thanks. After reading y'alls comments I'm even more convinced > that a terminal is the way to go, but have a bit of a supply > problem here in Mexico. Anybody know of dealers for > (preferably) Siemens terminals in the southern U.S.A. or > Mexico? Try http://tinyurl.com/4p7jh. John John Henderson <jhenRemoveThis@talk21.com> wrote in news:2nss22F4epc7U1@uni- berlin.de: >> ... no problem as long as we have the specs. > > They are available as PDF files (download free after > registering) from www.etsi.org. I'd suggest starting with GSM > specs 07.07, 07.05, 03.38 and 03.40. Oooh, what a wealth of information. :> >> Thanks. After reading y'alls comments I'm even more convinced >> that a terminal is the way to go, but have a bit of a supply [quoted text clipped - 3 lines] > > Try http://tinyurl.com/4p7jh Very nice. :> Thanks a bunch-- Larry John Henderson <jhenRemoveThis@talk21.com> wrote in news:2nss22F4epc7U1@uni- berlin.de: >> ... no problem as long as we have the specs. > > They are available as PDF files (download free after > registering) from www.etsi.org. A wealth of information. :> Anybody know of dealers for >> (preferably) Siemens terminals in the southern U.S.A. or >> Mexico? > > Try http://tinyurl.com/4p7jh. Very nice. Mmmm, now why didn't I find that? :> Thanks a bunch-- Larry > Thanks. After reading y'alls comments I'm even more convinced > that a terminal is the way to go, but have a bit of a supply > problem here in Mexico. Anybody know of dealers for > (preferably) Siemens terminals in the southern U.S.A. or > Mexico? You might want to consider Wavecom GSM terminals: http://www.wavecom.com/home/XMLindex.php. They seem to better regarded than Siemens, since Siemens reputedly outsourced firmware development. If I was buying one today, I'd go for the Wavecom (although I haven't used one). John John Henderson <jhenRemoveThis@talk21.com> wrote in news:2nvg4qF582soU1@uni- berlin.de: > You might want to consider Wavecom GSM terminals: > http://www.wavecom.com/home/XMLindex.php. > > They seem to better regarded than Siemens, since Siemens > reputedly outsourced firmware development. If I was buying one > today, I'd go for the Wavecom (although I haven't used one). *Very* interesting. And they have a branch in San Diego. :> Thanks for the info! I'll contact those folks. --Larry > *Very* interesting. And they have a branch in San Diego. :> > > Thanks for the info! I'll contact those folks. I've decided I'll probably buy a Wavecom unit myself soon (Fastrack 1206). Looking at the specs though, I'm not sure that Wavecom offer much for the 1900 mHz band used in Mexico/USA. John John Henderson <jhenRemoveThis@talk21.com> wrote in news:2o28qqF67hi5U1@uni- berlin.de: >> *Very* interesting. And they have a branch in San Diego. :> >> [quoted text clipped - 4 lines] > that Wavecom offer much for the 1900 mHz band used in > Mexico/USA. Well, I'm glad you mentioned that-- I'm very embarrassed to say I missed the frequency detail and was looking at the 1206 myself, which would have obviously been a problem. :-\ They do have the Q2426 module which runs 850/1900 mhz. From what I can see, nor does Siemens offer a 1900 mhz terminal though they have several tri-band modules which can be integrated. Mmmf, that adds a level of complexity that I hadn't anticipated. Wonder why these folks aren't (don't appear to be) offering 1900 terminals. Seems like a useful niche... Thanks-- Larry John Henderson <jhenRemoveThis@talk21.com> wrote in news:2o28qqF67hi5U1@uni- berlin.de: >> *Very* interesting. And they have a branch in San Diego. :> >> [quoted text clipped - 4 lines] > that Wavecom offer much for the 1900 mHz band used in > Mexico/USA. I've just been informed by the Brazilian Wavecom distributor that Multitech is producing a 1900 mhz terminal using the Wavecom hardware. Following that lead now... :-} Thanks-- Larry |
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