Abstract: An electronic ringer circuit suitable for use as a replacement for, or an alternative to, the electromagnetic ringer of a telephone set and other station apparatus is disclosed. To eliminate bell tap, each of the disclosed arrangements includes a load impedance that is connected across the output terminals of a rectifier-power supply stage until an acceptable ringing signal is detected. The load impedance is then disconnected and the signal provided by the rectifierpower supply stage activates a tone generator stage that drives a piezoelectric transducer. Various arrangements are provided, including configurations for single-party bridged ringing installations, multi-party divided ringing installations, coded ringing for use in situations wherein a number of stations are located in the same acoustic environment, and a multi-line installation such as a small key telephone installation.

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.