Abstract: A ringing signal control circuit used in a Subscriber Line Interface Circuit (SLIC) for connecting a ringing signal bus to a subscriber loop. The ringing signal bus transmits ringing signals along the subscriber loop to a subscriber instrument. The SLIC includes a High Voltage Line Interface (HVLI) circuit connected to the subscriber loop and the ringing signal bus is connected to a ringing generator that provides a source of ringing signals. The ringing signal control circuit comprises a logic interface circuit connected via an address/data bus to a central controller that is arranged to receive ringing connection signals from the central controller and to generate a ringing activation signal. A ring timing circuit receives the ringing activation signal and generates a first and second output signals. The second output signal is transmitted from the ring timing circuit at a specific time interval subsequent to the first output signal.

Abstract: An enhanced high voltage line interface circuit for a digital switching system over which a connection is established between a digital switching system and a subscriber instrument via a subscriber loop. The high voltage line interface circuit includes in combination circuits that provide power to the subscriber loop and convert received analog voice signals transmitted from the subscriber instrument into differential voltage voice signals for subsequent conversion to digital data for use by the digital switching system. Additionally, differential voltage voice signals from the digital switching system are converted to analog voice signals for transmission along the subscriber loop to the subscriber instrument. The high voltage line interface circuit further includes circuits that detect and monitor the subscriber loop status and develop digital logic output signals that are used to report the status of the loop to a digital switching system controller.

Abstract: An over-current verifier circuit used in a Subscriber Line Interface Circuit (SLIC) for validating an over-current condition on a subscriber loop comprising a first counter connected to the SLIC disposed to receive an oversense signal from the SLIC. The first counter begins counting when the oversense signal is received and produces an output signal when the oversense signal is still active after the counter finishes, denoting a dc over-current in the subscriber loop. A timer circuit connected to the SLIC also receives the oversense signal. The timer is arranged to begin counting when the oversense signal is received. A second counter further receives the oversense signal and is advanced by one count on the high to low transition of the oversense signal. The second counter produces an output signal when three counter advances are produced before the timer times out, denoting an ac over-current condition.

Abstract: An improved bi-directional buffer line amplifier is disclosed that provides a high performance analog interface between a Digital Network Interface Circuit (DNIC) and a transmission line. The buffer line amplifier includes a transmit amplifier network including an input connected to a DNIC transmit signal output. The input is arranged to receive transmit signals from the DNIC. A transmit output is connected to a matching network via a selectable gain amplifying circuit. The selectable gain amplifying circuit applies the transmit signals to the matching network in a first or a second gain level. In the first gain level the gain amplifying circuit is removed from the transmit amplifier network and the transmit amplifier network operates as a unity gain amplifier. This allows the buffer line amplifier to work efficiently with transmission line loop lengths from zero to a nominal distance.

Abstract: High impact strength resin compositions and methods of preparations thereof. The compositions contain at least 60% polyamide together with an elastomer and a polymeric emulsifier. The elastomer is preferably a copolymer of ethylene and an acrylic ester, and the emulsifier is preferably an ethylene/acrylic ionomer with at least about 50% of the carboxyl groups neutralized by displacement of a proton with a metal ion. In a particularly preferred embodiment, the polyamide is dispersed in a continuous elastomeric phase.