Abstract: The system has two units for transferring a telephone circuit from an old pair to a new pair between two locations. Each unit has a carrier amplitude measuring circuit to determine which location has the larger carrier amplitude and therefore which is the upstream location. Each unit has a charge switch, two transfer switches in the form of an old pair switch and a new pair switch and a controller for controlling the switches. One of the units closes its charge switch to charge the new pair to the dc level of the old pair. Then, the upstream unit operates its two transfer switches at the same time to switch from the old pair, by opening the old pair switch, to the new pair, by closing the new pair switch. The upstream unit transmits a signal to the downstream unit on a third pair. When the downstream unit receives the signal, it operates its two transfer switches at the same time to complete the transfer from the old pair to the new pair.

Abstract: The apparatus has a balanced capacitive probe for collecting a small portion of a carrier signal on a pair of wires. The collected portion of the carrier signal is mixed with a local oscillator signal so as to produce a heterodyned signal having a low frequency component and a high frequency component. The frequency of the local oscillator signal is selected to be within a few Kilohertz of the carrier signal so that the low frequency component is within an audible range. A low pass filter removes the high frequency component. The low frequency component is amplified and converted to sound. The audible signal is a representation of the carrier signal and allows a technician to determine the relative strength of the carrier signal and to identify the type of carrier signal on the wire pair. The probe enhances discrimination between uncoupled signals and coupled signals such as cross-talk.

Abstract: The apparatus has a probe for collecting a small portion of a carrier signal on a pair of wires. The collected portion of the carrier signal is mixed with a local oscillator signal so as to produce a heterodyned signal having a low frequency component and a high frequency component. The frequency of the local oscillator signal is selected to be within a few Kilohertz of the carrier signal so that the low frequency component is within an audible range. A low pass filter removes the high frequency component. The low frequency component is amplified and converted to sound. The audible signal is a representation of the carrier signal and allows a technician to determine the relative strength of the carrier signal and to identify the type of carrier signal on the wire pair.

Abstract: The invention provides methods of communication between two locations along a cable where the only metallic conductor available is grounded at numerous points along its length, which methods utilize a "distributed earth referenced carrier system" and wherein a first transceiver is electrically coupled to the metallic conductor at a first location and a second transceiver is electrically coupled to the metallic conductor at a second location.