Abstract: A data received is provided with DC restoration circuitry for correcting the DC level of received multi-level data signals. A DC shift detection circuit detects whether the received DC level multi-level signals has shifted due to a predominance of one of the data levels in the data stream. A correction circuit responds to the shift detection circuit by applying a corrective bias to an isolation transformer. Alternatively, the correction circuit applies a corrective bias to the received signals within the receiver circuit.

Abstract: A data transmitter circuit includes a pseudoternary conversion circuit for converting a binary logic signal to a differential pseudoternary signal having symmetric rise and fall characteristics. The output of the pseudoternary conversion circuit is filtered and passed to an electrically conductive medium via an isolation transformer. The conversion circuit includes a symmetric arrangement of toggle circuits which respond to transitions in respective complementary binary signals constituting a differential binary input signal. Voltage dividers are connected to the output terminals of the toggle circuits for providing three levels of output voltages in response to the logical states of the toggle circuits.