Abstract: A two to four wire hybrid converter for use in a telephone system that allows other telephone equipment, such as a caller identification device, to more readily decipher signals. The converter controls noise by using a digital to analog converter, hybrid circuit, interface circuit, and controller. The digital to analog converter accepts a receive digital data signal from a transmission line and converts it to a receive analog signal. The hybrid circuit accepts the receive analog signal and provides it to the customer telephone line, as well as accepting a transmit telephone analog signal from the customer telephone line. Such transmit telephone analog signals are then converted to digital signals and provided to the carrier transmission lines. The hybrid circuit includes an inverter, variable amplifiers, and summing circuit. The inverter inverts the transmit telephone analog signal with respect to the receive analog signal.

Abstract: A compensation circuit for adjusting the gain or loss of a four to two wire hybrid circuit in a telephone system automatically, regardless of the length of the telephone line interconnected to the hybrid circuit. The compensation circuit includes a converter, interface, gate array, and controller. The converter, which includes an amplifier with a variable gain, is connected to a digital carrier transmission line. The converter accepts a digital data signal and converts it to an analog intermediate signal. The interface receives the analog intermediate signal and transmits an analog telephone signal, along a customer loop telephone line, to a telephone. The interface also includes a pulse width modulated power converter for which the pulse width varies according to the length of the telephone line between the compensation circuit and the telephone. The gate array senses the pulse width and responsively provides a measured signal to the controller.

Abstract: A transmit path limiting circuit that allows other equipment, such as a caller identification device, to more readily decipher information signals on a telephone line. The circuit includes a ring detector, register, and controller. The ring detector senses that a call is incoming to the telephone and responsively provides an initiation signal. The register normally transmits outgoing signals from the telephone to the telephone network. After receiving the initiation signal, however, the controller enables the register, for a predetermined interval, to transmit a quiet code in lieu of any signal being transmitted from the telephone. Consequently, reflected noise is lowered during the predetermined interval, so that the caller identification box may more easily interpret data on the telephone line.

Abstract: A testing system for digital transmission lines with a metallic loopback and direct current bypass for use with regenerative repeaters. The Bell telephone network typically includes transmit and receive lines interconnected to a central office. Regenerative repeaters positioned along the lines detect signals and regenerate new signals. The present invention includes a controller, loopback line, and bypass. The loopback line interconnects the transmit and receive lines upon receiving a test activation signal from the controller. The bypass allows direct current to pass through to the rest of the line during a test. Accordingly, when a test of the telephone lines is to be performed, lines will allow the test signal to loop back to the source of origin, but will block the loopback of DC power signals. Moreover, DC power is supplied to the rest of the transmission line, in the same manner as when the testing procedure is not occurring.