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Technology Object of the Day – Modem

DUNUC 9354, instrument, Acoustic Coupler type TC301 (used as early form of modem) Two speakers into which telephone handset would be plugged to couple to another device. Computing Collection.

An acoustic coupler is an interface device for coupling electrical signals by acoustical means — usually into and out of a telephone instrument. The link is achieved through converting electric signals from the phone line to sound and reconvert sound to electric signals needed for the end terminal and back, rather than through direct electrical connection.

Acoustic couplers were sensitive to external noise and depended on the widespread standardisation of the dimensions of telephone handsets. Direct electrical connections to telephone networks rapidly became the preferred method of attaching modems, and the use of acoustic couplers dwindled

This Acoustic Coupler was donated to Museum Services by the School of Computing in 2005. Although intended to connect audio devices, it was used in the university as a modem to connect computers – but you had to be careful! Connecting too many computers at the same time was a major fire safety hazard!

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Credit: Copyright University of Dundee Museum Services,