Abstract: An apparatus for fault detection and coupled between a power supply line and a circuit to be powered. When a fault develops in the circuit that causes voltage in the power supply lines to decrease, the power being provided is interrupted from the circuit. Once the fault is removed, power is automatically returned to the circuit.

Abstract: A subscriber line interface circuit that provides regulated current to telephone subscribers in an improved manner reducing the amount of power required to operate while maintaining a constant current source. The current to the telephone subscribers flows through a switching transistor, an inductive storage element, sensing resistors and a transformer. The desired operating characteristic is obtained by cycling the switching transistor. The switching transistor is cycled on at a preset interval causing the telephone subscriber current to flow from the switching transistor. The switching transistor is cycled off in response to an increase in the telephone subscriber current as sensed by the sensing resistors thereby causing the current to flow from the inductive storage element.

Abstract: A telephone interface circuit for use in a digital loop carrier system. A transformer for coupling analog information and a switch responsive to a hook condition signal is provided. The hook condition signal provides an indication of the "on/off hook" condition of a corresponding telephone subscriber. The switch provides a closed circuit condition to "sink" a DC current when the corresponding telephone subscriber is "off hook" and an open circuit condition when the corresponding subscriber is "on hook". The telephone interface circuit further includes a capacitor serially coupled with the primary winding of the transformer, to prevent DC current from passing through the primary winding of the transformer. A combination telephone interface circuit that can be adapted for use as a remote terminal interface circuit or as a central office terminal interface circuit is also included. The combination interface circuit includes first and second circuit paths disposed in parallel with each other.

Abstract: A method and apparatus for reporting faults on a control line running through a plurality of processors to a control processor. Each processor having a failure provides a unique address onto the control line. The addresses are then sequentially shifted through each of the processors having a failure to the control processor.

Abstract: An integrated data voice multiplexer (IDVM) capable of simultaneously supporting loop-back and communication handshake protocols with no performance degradation. This allows the IDVM to be used in both point-to-point and packet switch networks. The IDVM is of the type using frequency shift keyed FSK modulation of two or more carriers to send a data signal. The presence or absence of carrier signals indicates loop-back state. Narrowband modulation is selectively added to at least one carrier to support handshake protocol. The preferred narrowband modulation is biphase at a rate lower than the FSK modulation rate. Encoder, decoder, data hold and detect circuits for supporting standard RS232 protocol are disclosed.

Abstract: A self-contained, pre-pay coin operated telephone wherein when the user removes a handset from a switchhook, a local dial tone is generated, prompting the user to enter a telephone number of a called party. Once the first digit of that telephone number has been entered, the locally generated dial tone is removed and the user completes the entry of the telephone number. Once the proper coin has been deposited, the internal computer causes the telephone to couple itself to a central office. The telephone number entered by the user is then sent to the central office under control of the internal computer. During this time, the microphone in the handset is muted such that the user cannot communicate through the telphone. Once the user hears the called party answering, then the user must actuate a push-to-talk switch to indicate to the computer that the party has answered.

Abstract: A T1 digital carrier system having a master terminal and four serially coupled remote terminals. Each remote terminal has a by-pass switch for automatically by-passing that remote terminal should a service threatening condition exist therein, thereby maintaining service to all remaining remote terminals. In addition, major and minor alarm information (indicating service requiring conditions) is transmitted by each remote terminal during signaling frames in the T1 serial bit stream.

Abstract: A self-contained, pre-pay coin operated telephone wherein when the user removes a handset from a switchhook, a local dial tone is generated, prompting the user to enter a telephone number of a called party. Once the first digit of that telephone number has been entered, the locally generated dial tone is removed and the user completes the entry of the telephone number. Once the proper coin has been deposited, the internal computer causes the telephone to couple itself to a central office. The telephone number entered by the user is then sent to the central office under control of the internal computer. During this time, the microphone in the handset is muted to disable communication. Once the user hears the called party answering, then the user must actuate a push-to-talk switch to indicate to the computer that the party has answered. The user is then allowed to speak to the called party and deposited coins are retained at the termination of the call.

Abstract: A power supply is provided with a predetermined nonlinear temperature coefficient for float charging sealed lead-acid batteries and providing power to a load. A temperature compensation network in the power supply provides the predetermined nonlinear temperature coefficient by using a linear temperature coefficient element (forward biased silicon diode) and a nonlinear temperature coefficient element (thermistor) in combination. Additionally, an over-voltage protection circuit, to disable the power supply should the output voltage exceed a predetermined value, is disclosed having a second temperature compensation network to compensate for the output voltage variation with temperature of the power supply.