Bell Telephone Laboratories

Micro Computer Systems, Inc.

Richard Scott Hoppough

Herbert B Walker

A disconnect signal (e.g. 130 volts D.C.) is applied at the telephone central office to the tip and/or ring lines. A latching relay adjacent to the subscriber equipment operates directly responsive to the disconnect signal, i.e. without delay normally caused by capacitive or voltage buildup, to disconnect the line between the tip and/or ring lines to which the signal has been applied and the subscriber equipment. The relay simultaneously connects the signal to ground through a relatively large resistance to identify or confirm to the central office that the switching action has occurred, which in turn is indicative of line continuity. The relay also operates in a similar manner responsive to a reverse polarity signal (e.g. the re-establishment of the normal line voltage of -48 volts D.C.) to re-establish a normal operative condition.

Telephone line/subscriber equipment disconnect apparatus

A signal is produced which is representative of the absolute value of the impedance of admittance (i.e., immittance) of a circuit as a function of frequency. At the same time, the frequencies are identified for the local maximum and minimum values of this signal.

Apparatus and method for determining frequencies for system maximum and

A controlled-amplitude, alternating test signal at a central office is applied to a telephone subscriber's line. The nonlinear impedance vs. voltage characteristic of the subscriber's telephone in an off-hook state causes harmonics of the test signal to be generated. A harmonic so generated is detected at the central office, which indicates the presence of a receiver-off-hook telephone.

Telephone receiver-off-hook detector

Apparatus which may be used in the performance of at least six tests on a telephone subscriber's line is disclosed. The apparatus operates to force the tip and ring leads of a line to particular potential levels and then produces output voltages related to the currents flowing in the tip and ring leads. These output voltages may be processed to perform the following test: dc Thevenin, ac three-terminal admittance, ac foreign emf, percent imbalance, swept loaded loop and detection of unauthorized equipment. The apparatus may be used when performing tests on other three-terminal circuits.

Apparatus for applying particular voltages to three-terminal circuits

A telephone line reported by a subscriber to be busy may be checked by the disclosed apparatus to determine if the telephone is actually in use or merely appears busy because of leakage in the telephone line or of the receiver being accidentally off-hook. When the telephone is actually in use, peaks in signals present on the line are counted and cause an in-use indication. When an accidentally off-hook or leakage condition is present, particular signals on the line or the absence of signals cause a not-in-use indication.

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Greensboro, NC, United States of America

Richard Scott Hoppough