Acoustic coupler

Prior to its breakup in 1984, Bell System's legal monopoly over telephony in the United States allowed the company to impose strict rules on how consumers could access their network.

When inventors began developing devices to send non-voice signals over a telephone line, the need for a workaround for the Bell restrictions was apparent.

Such modems or couplers were developed around 1966 by John van Geen at the Stanford Research Institute (now SRI International), that mimicked handset operations.

[5] One would dial the computer system (which would have telephone company datasets) on one's phone, and when the connection was established, place the handset into the acoustic modem.

Once direct electrical connections to telephone networks were made legal, they rapidly became the preferred method of attaching modems, and the use of acoustic couplers dwindled.

Acoustic couplers were still used until at least the late 1990s by people travelling in areas of the world where electrical connection to the telephone network was illegal or impractical.

An acoustic coupler (a Novation CAT 300 baud model) is prominently shown early in the 1983 film WarGames, when character David Lightman (portrayed by actor Matthew Broderick) places a telephone handset into the cradle of a prop acoustic modem to accentuate the act of using telephone lines for interconnection to the developing computer networks of the period—in this case, a military command computer.