A device onto which a telephone handset is placed to connect a computer with a network. The acoustic coupler might also contain a modem, or the modem could be a separate device.
Popular in the 1970s, acoustic couplers are no longer widely used. Nowadays, telephones connect directly to a modem via modular telephone connectors. This produces better connections than acoustic couplers and avoids the problems produced by irregularly shaped telephones. Still, acoustic coupler modems are useful in some situations, such as in hotel rooms where the telephone cable is anchored to the wall. Modems that do not use an acoustic coupler are sometimes called direct-connect modems.