TDD EMULATOR FOR A PERSONAL COMPUTER HAVING A SOUND CARD

摘要

Telephone Device for the Deaf (TDD transceiver) for a computing system and method of encoding and decoding TDD signals are described. The apparatus includes a sound card enabled to transmit and receive TDD coded Frequency Keying modulated audio signals. In extracting characters from a received audio signal, the sound card is used to sample the received audio signal. In extracting data bits from the received audio signal, groups of samples representing portions of the received signal are correlated against two frequencies.