Computers can be connected together in a network; but, increasingly, mobile computing requires that computers be able to access and connect to other computers from almost anywhere. This is possible through the use of telephone or cable systems and special computer communication devices called "modems" (Fig. 2.8.) "Modem" is short for "modulate-demodulate." The computer that, at the moment, is sending information uses its modem to "modulate" its electronic signal into a form that can be carried over the telephone or cable system; the computer receiving that information uses its modem to "demodulate" the signal. Information can be exchanged at speeds that allow effective long-distance computing.