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NowSMS Support Forums ⬆ NowSMS Support - SMS Issues ⬆ Archive through January 17, 2005 ⬆ |
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| Author | Message | |||
| Donato Unregistered guest |
I have a technical question... I am trying to control a industrial PLC (Programmable logic controller) using SMS. For this I will connect the PLC to a SMS Modem through a Serial port. My question is, Which modem will let me command the sending and receiving of SMSs through this port? i.e. The PLC sends a seiarl packet to the modem that says, send "text" to this number, etc. COnversely, when a SMS is received by the modem I want it to go to the PLC too (so it can be controlled remotely) The second question is, should I get a CDMA modem or a GSM modem? which service is available in the US (and who carries it?) Thank you very much | |||
| Bryce Norwood - NowSMS Support Board Administrator Username: Bryce Post Number: 3903 Registered: 10-2002 |
I'd go with a GSM modem, as long as it will go into an area with Cingular or T-Mobile coverage. (There are also CDMA modems, but the interfaces are not standard.) ETSI GSM 07.05 covers the AT command set for sending/receiving SMS. So you need a modem that implements that command set. There are quite a few of them, but admittedly, they are harder to come by in the US. Airdesk.net is a good source if you don't find any others. When looking at modems, you have to consider the US frequencies: T-Mobile uses GSM 1900, which a lot of tri-band modems will support. (Most tri-band devices are 900/1800/1900.) Cingular uses GSM 1900 and 850. 850 is pretty US specific. So if you're in an area that Cingular covers through that frequency, you need to make sure you have a modem that supports it. GSM modem manufacturers that target the US, such as Multitech, often have US versions that are dual band 850/1900, and Europe/Asia versions that are dual band 900/1800. (I haven't had any experience with any quad band modems, although I'm sure there are some by now.) -bn | |||
