Abstract: A bidirectional transmission path is typically coupled to unidirectional receive and transmit paths to effect amplification in repeaters or the like. A determination of whether the bidirectional path includes either loaded or nonloaded type 2-wire cable is made by inserting a test signal having a predetermined frequency and a predetermined amplitude into the receive path and measuring the peak amplitude of a transmit signal developed on the transmit path. If the transmit signal peak amplitude is greater than a predetermined threshold value, the 2-wire cable is considered loaded type, and if the transmit signal peak amplitude is less than the threshold value, the 2-wire cable is considered nonloaded type.

Abstract: "Transhybrid" loss is maximized in a transmission network of the active canceler type employed to couple receive and transmit unidirectional transmission paths to a bidirectional transmission path including 2-wire loaded type cable by controllably adjusting impedance elements of the canceler circuit in a prescribed sequence including adjustment of a network build out capacitor to obtain amplitude nulls of signals detected on the transmit path while supplying individual ones of a plurality of test signals to the receive path. The test signals include first and second signals having a plurality of equally spaced frequency components in first and second frequency bands, respectively, and a third signal having a predetermined single frequency.

Abstract: "Transhybrid" loss is maximized in a transmission network of the active canceler type employed to couple receive and transmit unidirectional transmission paths to a bidirectional transmission path including 2-wire nonloaded type cable by controllably adjusting impedance elements of the canceler circuit in a prescribed sequence to obtain amplitude nulls of signals detected on the transmit path while supplying individual ones of a plurality of single frequency test signals to the receive path. The adjustment sequence comprises a first procedure including a plurality of iterative adjustments of predetermined impedance elements in predetermined groups until no changes in the impedance settings occur and multiple iterative adjustment of predetermined groups until no changes in the impedance settings occur.

Abstract: Hybridless bidirectional transmission networks typically include telephone line coupling transformers and unidirectional amplifiers for enhancing outgoing and incoming signals. Unwanted signal components in the outgoing direction, caused by cross coupling via the transformer of incoming signals, are minimized by employing a canceller network in circuit with the incoming and outgoing amplifiers. The canceller network has a complex transfer characteristic to compensate substantially for complex impedance components of the coupling transformer and 2-wire transmission facility and to generate a signal which is substantially a replica of the unwanted outgoing signal components. The replica signal and unwanted signal components are algebraically combined in the outgoing amplifier effectively to eliminate the unwanted signal components from the outgoing path.