Ven-Tel and Anderson-Jacobson
acoustically coupled modems
Acoustic coupler in action with DEC VT520 terminal
IBM PC/AT with Hayes Smartmodem
Ven-Tel and Anderson-Jacobson acoustically coupled Bell 103 modems, 1970s
(we also used to have some A-J wooden models but they were thrown out before
I could photograph them). To make a connection, you dial the number on the
telephone, wait for the tone from answering modem, then mash the telephone
receiver down into the rubber cups as shown at right, at which point the
Carrier light should come on and you can start using your connection. There
is no autodialer, no no error detection, no error correction, no
compression. The 25-pin serial interface is at the rear and operates at 110
or 300 bits per second depending on the answering tone. Beginning in the
1980s, "smart" modems like the one shown at right dispensed with the rubber
cubs, and were connected to the telephone's RJ45 jack.
