SD Sales cassette interface, 1977

Summary

SD Systems produced an audio cassette interface card in 1977, to store and recall programs run on microcomputers. See my Web page on other ways audio cassettes were used with microcomputers of the era. - Herb Johnson

In 1977, SD Sales produced an interface card for an audio cassette recorder player to store and recall binary data for any microcomputer. The card has simple circuits to generate and detect the "Kansas City" standard tones of 1200 Hz and 2400 Hz to represent binary 1's and 0's. The kit included all components; SD Sales pre-built portions of the circuits to assure they would be tuned to those frequencies. An interesting update from SD Sales included a replacement resistor as their early kits were mis-tuned. See the card's manual for details. Manual courtesy of Howard Harte's S-100 manuals Web site.

SD Sales produced a number of S-100 cards for microcomputers of the 1970's, and other microprocessor-supporting products. They were one of hundreds of S-100 computer producers of the period,, among dozens of other types of microcomputers and producers, large and small, in the 1970's.

- Herb Johnson