<hardware, communications> A device used to connect a modem to a telephone line via an ordinary handset. The acoustic coupler converts electrical signals from the modem to sound via a loudspeaker, against which the mouthpiece of a telephone handset is placed. The earpiece is placed against a microphone which converts sound to electrical signals which return to the modem. The handset is inserted into a sound-proof box containing the louspeaker and microphone to avoid interference from ambient noise. Acousitic couplers are now rarely used since most modems have a direct electrical connection to the telephone line. This avoids the signal degradation caused by conversion to and from audio. Direct connection is not always possible, and was actually illegal in the United Kingdom before {British Telecom} was privatised. BT's predecessor, the General Post Office, did not allow subscribers to connect their own equipment to the telephone line. (1994-11-08)

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Buffers and chain couplers (also known as "buffers and screw", "screw", "screwlink", and "English" couplers) are the de facto UIC standard railway stock coupling used in the EU and UK, and on some surviving former colonial railways, such as in South America and India, on older rolling stock. Buffers and chain couplers are an assembly of several devices: buffers,EN 15551:2009+A1:2010 Railway applications – Railway rolling stock – Buffers hooks and links, or turnbuckle screws.

A rat-race coupler, also known as a hybrid ring coupler, is a type of coupler used in RF and microwave systems. In its simplest form, it is a 3 dB coupler and is thus an alternative to a magic tee.

Acoustic shock is the set of symptoms a person may experience after hearing an unexpected, loud sound. The loud sound, called an acoustic incident, can be caused by feedback oscillation, fax tones, or signalling tones.

Acoustic microscopy is microscopy that employs very high or ultra high frequency ultrasound. Acoustic microscopes operate non-destructively and penetrate most solid materials to make visible images of internal features, including defects such as cracks, delaminations and voids.