This is an ISA expansion card that was originally designed for type approval of voice codecs for a satcomms system. Some of these have a 2-wire handset interface only. The DAA card provides 2-wire to 4-wire conversion, ring signal detection, and DTMF code generation and detection. It also provides accurate gain control. All functions are accessible via the PC software. Both a stand-alone command-line control program and a C device driver were supplied.
An 87C552 processor provides all time-critical functions, therefore no stringent real-time demands are placed on the host PC.
This card was designed to be a generic phone line interface, and has been used in several Giastar systems in addition to the codec test set it was initially intended for.
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