Abstract: A multi-speed, full duplex modem is disclosed for transmitting and receiving analog signals over a telephone network in communication with a remote modem. The analog signals are converted to digital data for processing by a signal processor and a microcomputer. A bi-directional bus is disposed between the signal processor and the microcomputer for selectively transferring multiple bits of data in either a transmit or receive direction. One or more of the multiple bits of data are restricted to convey bus direction data in one of the transmit and receive directions, and not restricted in the other direction. The full duplex modem allows simultaneous transmission and reception of analog signals over the telephone network, at one of the multispeed data rates selected for compatability between the full duplex, multispeed modem and the remote modem.

Abstract: A dual speed, full duplex modem for transmitting and receiving data on a dialed-access telephone line includes a signal processor for storing samples corresponding to a sinusoidal waveform, for selecting samples at intervals determined by the mode in which the modem is operating to synthesize a signal for modulating by data for transmission, and for autocorrelating a received signal at a frequency determined by the mode in which the modem is operating to recover data from the received signal. The signal processor includes configuring input ports, and a microcomputer receives instructions related to the mode in which the modem is to operate to output a mode-configuring word to the configuring inputs. Conversion from the signal processor's digital output to the analog signal to the line and from the line's analog signal to the signal processor's digital input take place through two time-division multiplexed coder-decoders. The stored sinusoid is mu-law compressed.