Abstract: An instant telecommunications network backup system includes several trunk diverter circuits and several responder circuits. Each trunk diverter circuit is installed proximate to an originating central office within the telecommunications network and monitors an outgoing trunk for faulty conditions. The trunk diverter circuit maintains a database that classifies each responder circuits as being in one of two classes: a maintain link class and a disabled class. One or more responder circuits are installed proximate to an emergency response facility. Whenever a faulty condition is detected, the trunk diverter circuit establishes an alternative telecommunications path through either a public switch telephone network or a mobile telephone switching network to one of the responder circuits in the maintain link class. The trunk diverter circuit and the responder circuit exchange communications with each other.

Abstract: A line lifting apparatus is disclosed which functions to connect and disconnect a customer station and a telephone line extending from a central office to the customer station, for line testing purposes. The connection and disconnection is provided by a bistable latching relay which is controlled by a control circuit responsive to potentials impressed on the conductors of the telephone line. A first potential applied to either or both of the conductors of the telephone line causes the control circuit to place the bistable latching relay in a state wherein the telephone line is disconnected from the customer station, and a second potential applied to either or both of the conductors of the telephone line causes the control circuit to place the bistable latching relay in a state wherein the telephone line is connected with the customer station.

Abstract: An electromagnetic sensing apparatus includes one or more magnetic cores coupled by windings to a pair of transmission line conductors for sensing the presence, and in some cases the magnitude and direction of loop currents flowing in the transmission line, without interfering with the transmission of signal information therealong. In one embodiment, the direction of loop current flow in the transmission line conductors is detected by applying a steady-state electromagnetic bias to the magnetic core to cause a polarity or direction determining asymmetrical response in a sense circuit that is electromagnetically coupled to the core by a sense winding. In another embodiment, a pair of separate magnetic cores are used, each having associated drive windings connected in series with the transmission line conductors, and associated sense windings.

Abstract: After description of a number of prior art automatic telephone number identification systems and certain problems associated therewith, a new method and apparatus for use in such systems which overcomes the problems of the prior art is described. In its preferred form, the method includes the steps of applying to the telephone line at a central office a voltage which has a magnitude sufficient to produce a first predetermined value of loop current in the telephone line. At each party station, the loop current is caused to change between the first predetermined value and a second predetermined value in a manner unique to that party station, with the second predetermined value being smaller than the first predetermined value but greater than a value of loop current that would signify to the central office that an on-hook condition exists on the telephone line.

Abstract: A switching control signal switches a pair of emitter coupled transistors via a drive circuit jointly connected to the base electrodes of the transistors so as to drive the base-to-emitter junctions between an "on" condition in which both base-to-emitter junctions are forward biased and an "off" condition in which both base-to-emitter junctions are reverse biased. In the "on" condition, the collectors of the transistors simulate closed relay contacts capable of conducting substantial current flow and in the "off" condition the collectors simulate open relay contacts capable of accomodating substantial standoff voltages. The drive circuit which controls the "on" and "off" conditions of the transistors includes separate turn "on" and turn "off" circuit paths for producing fast and uniform switching characteristics at the collectors.

Abstract: An identification circuit, which is useful in a communication system comprising a plurality of remote stations and one central station, for automatically distinguishing between two remote stations in the system which are common to a single communication line pair connection to the central station. A two-party telephone line in a telephone network is an example of such a system. The identification circuit includes a ground mark circuit which in turn includes sufficient dc resistance to provide an electrical imbalance on the communication line pair when the ground mark circuit is connected between the communication line pair and ground. A sensing circuit and a control circuit are also provided, with the sensing circuit being responsive to a dc current in a portion of the communication line pair connected to a selected one of the two remote stations to energize the control circuit, which is in turn operable to connect the ground mark circuit between the communication line pair and ground.

Abstract: In order to distinguish voice and other noise signals which may be present on telephone or similar communications lines from legitimate multi-frequency tone data and control signals, three detectors are disclosed. A frequency drop detector is provided which receives an input from the lines and which provides an output signal upon receipt of any signals appearing on the lines which terminates when the frequency thereof rapidly drops by a predetermined amount. Means consisting of a long-time interval detector are provided for investigating the status of the frequency drop detector's output for a predetermined time after the production of said output signal. If the output signal from said frequency drop detector is provided throughout said predetermined time period, the signal on the lines is defined as legitimate and a circuit output signal is produced. In all other cases, the circuit output signal is inhibited.