Most road warriors have learned that laptops won't work on the digital phone systems found in some hotels. But did you know that simply plugging your phone card into a wall jack can fry a credit-card-style modem? The popular micromodems lack the mechanical relays that protect bigger modems from the high voltages present on some digital systems. Jacks marked "data" are usually safe. But when in doubt, check with hotel management before plugging in.

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