A GSM modem is a wireless modem that works with a GSM wireless network. The main difference between GSM modem and dial-up modem is the medium of sending and receiving data. Dial-up modem sends and receives data through a fixed telephone line while a wireless modem sends and receives data through radio waves.
A GSM modem can be an external device or a PC Card / PCMCIA Card. Typically, an external GSM modem is connected to a computer through a serial cable (RS232) or a USB cable. Like a GSM mobile phone, a GSM modem requires a SIM card from a wireless carrier in order to operate.
Computers use AT commands to control the GSM modems. Both GSM modems and dial-up modems support a common set of standard AT commands. In addition to the standard AT commands, GSM modems support an extended set of AT commands. These extended AT commands are defined in the GSM standards. With the extended AT commands, GSM modem can do:
- Reading, writing and deleting SMS messages.
- Sending SMS messages.
- Monitoring the signal strength.
- Monitoring the charging status and charge level of the battery.
- Reading, writing and searching phone book entries.
The number of SMS messages that can be processed by a GSM modem per minute is very low - only about six to ten SMS messages per minute.
Source : Developer's Home
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