RS232 Serial Cable and Industrial Modems

This page provides information about the use of an RS232 data cable, as well as about some of the most reliable GSM devices you can attach to your computer for SMS messaging using the Ozeki NG - SMS Gateway software.

In order to send and receive SMS messages from your PC, you can attach your phone to the PC with a phone-to-PC data cable (Figure 1). The cable is attached to the serial port of your computer. The serial port is located on the backside and has 9 pins. The name of the serial port in your operating system is COM1 or COM2.

If you have different options (e.g., Serial, USB, IR, BT connection), choosing the serial cable is a good choice. An RS232 serial data cable is a simple and reliable tool. The newest modems use USB data cables. Industrial GSM modems used in environments where performance and reliability are crucial are always connected using RS232 or USB cables.

If you wish to build an environment where continuous operation is important, you should use an industrial GSM modem (Figure 2):

	Multitech SMS modem MultiTech MultiModem is a very fast and reliable modem. The modem has an external GSM antenna, an USB data cable. It can be connected directly to the power supply of your PC. To find out more about the modem, check out the MultiModem EDGE wireless modem page. To find out how to attach a MultiTech MultiModem and how to install a standard modem driver, check out the Installation of a MultiTech MultiModem page.
	Sierra Wireless AirLink Fastrack Sierra Wireless delivers a very good modem. These modem works with an external GSM antenna, an USB data cable. It can be connected directly to the power supply of your PC. To find out more about the modem, check out the Sierra Wireless AirLink Fastrack Xtend EDGE Modem, FXT009 page. To find out how to attach a Sierra Wireless AirLink Fastrack modem and how to install a standard modem driver, check out the Installation of a Sierra Wireless AirLink Fastrack modem page.
	WAVECOM Wavecom provides very fast and reliable modems for a good price. These modems need an external GSM antenna, an RS232 data cable. Just like the Siemens MC35, they can be connected directly to the power supply of your PC. To find out more about the modem, check out the Wavecom Fastrack page. To find out how to attach a Wavecom modem and how to install a standard modem driver, check out the Installation of a Wavecom modem page.
	Fargo Maestro 20 Fargo Maestro is a reliable GSM modem. You can read more about it on the Maestro 20 page.
	Fargo Maestro 100 Fargo Maestro is also a reliable GSM modem. You can read more about it on the Maestro 100 page.
	SIEMENS TC35 / SIEMENS MC35 An excellent GSM phone released by Siemens. It can be connected directly to the power supply of the PC. It uses an external antenna, and it has a standard 9 pin RS232 interface. You need a standard RS232 "mouse extender" cable to connect this device to the PC.
	NOKIA 30/ Nokia 32 Nokia 30 is also an excellent GSM phone. You can read more about it in its installation guide: Nokia-30-GSM-modem-terminal.pdf

Figure 2 - Industrial GSM modems

To find out more about suitable GSM devices, check out the Supported Phones page.

FAQs

My modem usually works for one or two hours without a problem, then I see timeout messages in the log. What causes this problem?

It sounds like you might be experiencing a hardware problem, most likely with the modem itself. While less common, the USB to RS232 converter could also be a factor.

The issue manifests as the modem becoming unresponsive to the computer after some time.

Some modems, especially older models or those with buggy firmware, struggle to handle the Ozeki software's continuous communication style.

Ozeki SMS software maintains constant communication with the connected modem. It constantly checks the modem's memory for incoming messages, downloading and deleting them upon discovery. This continuous activity might overwhelm some modems.

We recommend replacing your current modem with a Wavecom Supreme 10 model. This model is known to be more reliable and handle the software's communication style effectively. In essence, the issue might stem from the modem's inability to keep up with the software's demands. Upgrading to a more robust model like the Wavecom Supreme 10 can potentially resolve this.