| 摘要 |
<p>The present invention relates to a method of transmitting speech and digital data via an analog speech channel (4) within a single frequency band. An analog speech signal is transmitted (20) via the speech channel (4), and a stream of digital data is encoded (21, 22, 23) by means of an encoding device (5) to a sequence of blocks of symbols, with each symbol taken from a predetermined set of symbols. The transmission of the analog speech signal is periodically blanked (24) during predetermined spaced time intervals (40), and the blocks of symbols are transmitted (25) during the time intervals (40). In each time interval (40) a plurality of signals are transmitted via a corresponding plurality of spaced predetermined carrier frequencies (50). Each block of symbols is transmitted during a different time interval group (41), each consisting of the same predetermined number of the time intervals (40). For each block of symbols all symbols from the respective block are uniquely associated with one of the predetermined carrier frequencies (50) in one of the time intervals (40) of the respective group (41), and each such carrier frequency (50) is modulated such that the signal transmitted via the respective carrier frequency (50) assumes one of multiple predetermined conditions representative of the respective symbol. A receiver (8) is used (26) to receive the analog speech signal and the signals transmitted during the time intervals (40). The signals are demodulated (27) to recover the individual symbols and the respective block of symbols transmitted during the time interval groups (41), and the recovered blocks of symbols are decoded (28) to recover the digital data.</p> |
