acoustic coupler
acoustic coupler - “A type of *modem that converts serial digital data into a *frequency shift keyed sound signal in the audio range for transmission down telephone lines, and decodes similar incoming sound signals. The connection between the acoustic coupler and the telephone system is made by means of a small microphone and loudspeaker held close to the earpiece and mouthpiece of an ordinary telephone handset in a sound-absorbent enclosure.” (Fair Use ODCS)
“Although largely superseded by devices that connect directly to the telephone network, acoustic couplers are still used. The lack of any electrical connection between terminal and phone lines was of benefit when obtaining the approval of the PTT for the use of such a device. The quality of ordinary switched voice circuits normally limits the transmission speed to 300 baud or less.” (Fair Use ODCS)
- Snippet from Wikipedia: Acoustic coupler
In telecommunications, an acoustic coupler is an interface device for coupling electrical signals by acoustical means—usually into and out of a telephone.
The link is achieved through converting electric signals from the phone line to sound and reconverting sound to electric signals needed for the end terminal, such as a teletypewriter, and back, rather than through direct electrical connection.