Digital data communication system featuring multi level asynchronous duplex operation

In a system for transmitting and receiving digital data signals using a single transmission line, improved means coupled to one end of said line capable of transmitting a first multi-level signal representative of a first plurality of individual digital data signals while simultaneously receiving and decoding at said one end a second multi-level signal representative of a second plurality of individual digital data signals, said improved means comprising:

• transmitting means for converting said first plurality of digital data signals into said first multi-level signal and for applying said first multi-level signal to one end of said transmission line for transmission thereby;
• a plurality of unclocked receivers coupled to said one end of said transmission line, one for each of the levels of said second multi-level signal, each receiver having a bias-controllable threshold chosen so that the receivers together provide for detecting all of the levels of said second multi-level signal;
• logical decoding means coupled to the outputs of said receivers for producing decoded digital signals representative of said second plurality of individual digital data signals;
• and
• dynamically variable biasing means responsive to a first multi-level signal being transmitted by said transmitting means for controlling the biasing of said receivers so that the thresholds provided thereby appear substantially constant to a received second multi-level signal even during simultaneous transmission of a first multi-level signal by said transmitting means.

A method for the simultaneous transmission and reception of multi-level signals at one end of a transmission line wherein the transmitted and received multi-level signals are each representative of a corresponding plurality of individual digital data signals, said method comprising the steps of:

• converting a first plurality of digital data signals into a first multi-level signal;
• applying said first multi-level signal to one end of said transmission line;
• decoding a second multi-level signal received at said one end of said transmission line by steps including detecting the levels of the received multi-level with reference to predetermined threshold values chosen so as to produce resulting digital signals representative of a second plurality of individual data signals;
• dynamically varying said predetermined threshold values in accordance with the instantaneous value of a transmitted multi-level signal so that the thresholds appear substantially constant to a received multi-level signal even during simultaneous transmission of a first multi-level signal from said one end of said transmission line;
• and
• filtering said resulting digital signals by removing therefrom spurious pulses having a significantly shorter duration than that of said resulting digital signals.

A method providing for the simultaneous bidirectional transmission of a plurality of asynchronous individual digital data signals using a single transmission line, said method comprising the steps of:

• converting a first plurality of individual data signals into
• a first multi-level signal and applying said first multi-level signal to one end of said transmission line;
• converting a second plurality of individual data signals into a second multi-level signal and applying said second multi-level signal to the other end of said transmission line;
• decoding a received multi-level signal at each end of said transmission line by steps including detecting the levels of the received multi-level signal with reference to predetermined bias-controllable threshold values chosen so as to produce resulting digital signals representative of the corresponding plurality of individual digital data signals transmitted from the other end of the transmission line;
• dynamically varying the biasing of said predetermined threshold values at each end of the transmission line in accordance with the instantaneous value of a multi-level signal being simultaneously transmitted from that end so that the thresholds at each end appear substantially constant to a received multi-level even during simultaneous transmission and reception of a multi-level signal at each end;
• and
• filtering the resulting decoded digital signals by removing therefrom spurious pulses having a significantly shorter duration than that of the resulting decoded digital signals.