Connecting To ABBS Through An Acoustic Coupler At 300 Baud
| Field | Digital Communication & Data Transfer |
| Went Obsolete | c 1979 |
| Made Obsolete By | The introduction of the Hayes Micromodem II and later the Smartmodem. As well as the deregulation of the telephone industry. 300 baud acoustic couplers lived on with cheap computers well into the 1980s, however; they were far cheaper to make |
| Knowledge Assumed | Basic computer and keyboard skills |
| When useful | This was the essential first step toward modern digital interconnectivity and communication of the masses |
The first thing one had to keep in mind was that back in the 1970s, it was illegal to connect equipment up to the telephone company that was not rented directly from them. Thereby, in order to get around this rule, acoustic couplers were introduced.
Another thing to keep in mind was that all early acoustic modems lacked a Microprocessor and purely used discrete components to modulate and demodulate data. These modems were typically used with "Dumb" terminals and were around as early as the mid 1960s.
The typical acoustic modem had two lights, a "Power" light and a "Carrier" light, as well as a switch for power. Some acoustic modems also had DIP switches so you could set things like Baud Rate to your serial port, as well as Bits per Charactor, Stop bits and Party Bits. Most BBS systems used 8 data bits, 1 stop bit and no parity. As well, by the mid 1980s, some BBS systems started to prohibit 300 baud connections as 300 baud users tended to be younger and had a demographical reputation of causing trouble for the sysop and other users.
On the top of the modem are two "Cups" that are the same shape as a standard telephone receiver. These were round, although some later ones used square cups, but these are rare.
To dial a BBS, one simply picked up the phone and dialed it, just like they would if they were talking to someone. Once you heard the carrier on the other end of the line (It would have a loud and annoying tone) you simply took the receiver and placed it directly into the cups so that the receiever sat ontop of the modem. (Listening side on the top, talking side on the bottom.)
Once the modem detected a carrier, the "Carrier" light would come on and communications would begin. To "Hang up", all you had to do was take the receiver off the modem and hang it up on the phone itself,
The big problem with acoustic couplers is that they are not perfect. Any loud noises in the room would cause noise to be introduced into your session and result in garbled charactors. Thereby, the option to listen to loud Black Sabbath while sending electronic e-mails simply was not there. As baud rates increased, these modems became increasingly sensitive to noise.
The introduction of the Hayes Micromodem II in 1979 eliminated the need for acoustic couplers as it directly connected to a phone line. However, since it lacked a speaker, a speakerphone was needed to obtain the status of the call. (ie. Such as obtaining a busy signal) The need for a speakerphone was eliminated with the introduction of the Hayes Smartmodem in 1980, since it already had a speaker included. Most computer users could not afford such wonders, however. Computers such as the TRS-80 or C64 were usually mated with a 300 baud acoustic couple modem, and firms continued to sell these old-design modems through magazines into the late 1980s, often for as little as $30.