Digital phone systems can fry PCMCIA modems

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Check to see which type of phone system you have before you connect a PCMCIA modem to it. The newer digital systems send out a series of high-current signals when a device is first connected to it. This current may be high enough to overload and burn out the solid-state relay in a PCMCIA modem. Unfortunately, both types of systems use RJ-11 connectors, making it difficult to tell them apart.

Some solutions were suggested by Bill Machrone in recent PC Week articles. First, ask about the system you are connecting to. Rolm, Northern Telecom, and others have digital systems. Second, use a modem adapter which connects through the handset cord. Finally, IBM markets a device called the "Modem Saver" (Part Number 73G5395, $29). This pen-sized device plugs into an RJ-11 socket and its LEDs tell you whether you have a normal, high-current, or reversed polarity line. (Reversed polarity can effect high-speed modems, resulting in greater error rates.)

Rich Hall Editor, HP Palmtop Paper