Abstract: An electromagnetic device utilizing a Hall effect switch for detecting the presence or absence of an electrical current. The device includes a flux generator for generating a field of magnetic flux and an adjustable magnetic circuit for varying the amount of flux delivered to the Hall switch.

Abstract: A circuit which can perform a plurality of sensor functions relating to telephone subscriber supervisory circuits. These functions can occur before and after ringing current is applied to the subscriber line facility. Coils function as magnetic field generating devices and a Hall effect device is used to perform the sensory functions. A programmable comparator is used to compare detected conditions with predetermined thresholds.

Abstract: A contactless electromagnetic relay employing at least two magnetically activated electronic switches comprising a coil for generating a field of magnetic flux in response to an electrical current and a pair of magnetic circuits for conveying the flux to the switches. A first switch is "normally on" and a second "normally off" when no flux is generated by the coil, providing a first switching state. A second switching state is achieved by the relay when the coil generates a magnetic flux sufficient to turn off the first switch and turn on the second switch. Each magnetic circuit includes an adjustable core for increasing or decreasing the amount of flux delivered to each switch.

Abstract: A circuit which detects the presence and absence of a telephone subscriber loop, before and after ringing current is applied to the loop. Coils functioning as magnetic field generating devices and a Hall effect device are used to perform the detection function. Inclusion of a capacitive shunt network limits the responsiveness of the Hall effect device during ringing, permitting use of the device on lines to which multiple ringers are connected.

Abstract: A circuit which detects the presence and absence of a telephone subscriber loop, before and after ringing current is applied to the loop. Coils functioning as magnetic field generating devices and a Hall effect device are used to perform the detection function.