Abstract: A digital signal processor is provided with the facility to range and converge on each of a plurality of echoes occurring at respective locations along a communications line. Specifically, the digital signal processor is arranged to adaptively process samples of a signal that has been transmitted to the communications line correlated with samples of a signal that have been received from the communications line. In the processing of the samples, the digital signal processor separates and measures the magnitude of each echo that it converges on, beginning with a so-called near-end echo. In addition, the digital signal processor calculates the propagation delay of each echo that it converges on using the number of sampling intervals that have been processed in order to position the processor on the dispersion of that echo.

Abstract: A selective call communication system for use by an untrained person is provided. The communication system includes a number of telephones located in different locations, connected to a central switching unit. A number of selective call radios, each having an address, are assigned to the central switching unit. Upon the use of the telephone, the central unit identifies the telephone in use, and initiates an alerting call to the corresponding selective call radio automatically. The selective call radios may be pagers or two-way radios. Other features such as radio to radio communication, and radio to telephone network communication may be incorporated into the system.

Abstract: An individual subscriber circuit protector module employing solid state circuitry for protection against momentary voltage surges, and having firmly sensitive heat coil assemblies for protecting against continuous excess current surges. Fail-safe protection is also provided which becomes operative in the event of failure of the heat coil protection.

Abstract: A projection of a retaining element swivel-mounted inside a base part of a telephone set projects through the region of the cradle for the handset of the telephone set. The projection engages in a recess of the handset. The retaining element is directly connected with the switch bar for the cradle switch, swivel-mounted and under spring tension.

Abstract: A telephone line interface circuit includes a transformer with tip and ring windings connected between tip and ring feed resistors and tip and ring leads of a telephone line for feeding energizing current from telephone facility to the telephone line. A secondary winding in combination with the tip and ring windings couples a.c. signals between the facility. A capacitance is connected in combination with the secondary winding to simulate a function of a capacitance as would normally be connected between the tip and ring windings in prior art circuits, but without the problem of feed resistor interference at lower voice band frequencies. Network and component values are inserted between the secondary winding and an electronic hybrid circuit whereby the line circuit is precisely tailored for anyone of several national telephone line standards.

Abstract: An amplification device which enables an electret handset microphone, a dynamic handset microphone, or a carbon handset microphone to be connected to either an electronic telephone or to a hybrid coil telephone. The amplification device is powered from current from the line connecting the telephone to a KSU, PBX, or other telephone servicing system.

Abstract: A pair of interface devices, mounted externally to a pair of residential telephones, can place a temporary hold on the associated telephone line circuit. Each interface device interconnects a standard residential telephone with an associated telephone line circuit. In a two telephone arrangement to place the telephone circuit in a hold condition, the user throws a switch mounted on the interface device, and hangs up the handset (goes on hook). The switch places two indicator lamps across the two-wire line circuit to simulate an off-hook condition. To remove the hold condition, the user merely throws the same switch or the switch associated with one of the other phones in the residence. There is no need to return to the original phone first used to establish the hold.