From June Langhoff, author of Aegis Publishing Group's Telecom Made Easy and Telecommuter's Advisor , here are seven easy steps for hot-wiring your modem. First, you must be certain the phone line is analog, not digital. Plug in to a digital line, and you can kiss your modem goodbye. Other indications are multiple push buttons, visual displays, built-in voice mail and keypads with special dialing or function buttons. Your safest bet is to test the line.
Seasoned travelers carry a testing device that can insert into the jack.
Remove the cover plate over the phone connection at the wall. Inside you will most likely see four colored wires. Select two of the wires to test for a phone signal. Attach one alligator clip to each wire. To determine which of these wires carries the phone signal, insert your line tester into either end of one of the alligator clips.