Abstract: A distribution network power line communication system divided into addressable communication zones defined by signal repeaters located at spaced intervals along the distribution network. The signal repeaters are switchably disposed in signal communication between the primary and grounded neutral conductors of the primary distribution network. Each repeater, when uniquely addressed by an interrogation signal from a central communication terminal, transfers the interrogation signal from the primary conductor to the primary grounded neutral conductor whereon it is transmitted to a uniquely addressed remote communication terminal coupled to a secondary neutral conductor within the communication zone of the signal repeater. A timely response signal from the remote communication terminal on the grounded neutral conductor is transferred by the repeater to the primary conductor and then to the central communication terminal.

Abstract: An input signal supplied to a signal measuring circuit is either amplified or attenuated as necessary to establish the magnitude of the input signal within the defined dynamic range of the measuring circuit and the output signal developed by the measuring circuit is subsequently readjusted through amplification or attenuation to develop an output signal which corresponds to the magnitude of the initial input signal.

Abstract: A transducer is utilized to convert the eccentricity of a turbine shaft into a sinusoidal electrical voltage signal having a given frequency, amplitude and a DC bias. This electrical signal is provided to a circuit which periodically measures the maximum and minimum peaks of the sinusoidal signal. The frequency at which the latter measurements occur is related to the frequency of the sinusoidal input signal. The maximum and minimum levels of magnitude are stored periodically as DC levels and subtracted from each other to determine the absolute value of eccentricity. In addition the stored minimum value is compared with the sinusoidal signal to reduce the DC bias of the sinusoidal signal to a point where the negative peaks thereof are at zero.

Abstract: Signal input devices and systems which include a switch, a continuously energized light source, and an electro-optic light valve disposed between the back of the switch and the light source. The electro-optic light valve is operable between light transmitting and light blocking conditions, with the electro-optic light valve being switched from one of its conditions to the other in response to actuation of the switch. The switch is constructed to enable light from the light source to be visible on the front or actuating side of the switch when the electro-optic light valve is light transmissive. A plurality of devices may be grouped with a common light source, to provide an electronic keyboard, or other signal input station or panel. A specific application of a group of signal input devices used as a call input station in an elevator system is also disclosed.

Abstract: The disclosure relates to a time-overcurrent relay utilizing successive linear time-current segments which approximate a non-linear, inverse time-current curve the linear segments are determined by subtracting a series of ramp like voltages of increasing magnitudes from a series of bias voltages, each of which is of substantially constant magnitude and which bias voltage magnitudes decrease in sequence by the peak magnitude of the preceding ramp voltage.

Abstract: Carrier current signals are impressed to and detected from grounding conductors connected to the power system and to real earth ground. The communication links provided by the grounded neutral conductors of the power system and by the real earth ground return path transmit the carrier communication signals between a substation communication terminal and remote communication terminals at the premises of utility company customers. The communication signals are coupled to the ground conductors by transformer-type couplers in which the grounding conductor constitutes one winding of the transformer.

Abstract: Methods and apparatus for identifying the source location of acoustic emissions generated within or on an acoustically conductive medium segregated into a plurality of quadrilateral monitoring zones. A plurality of acoustic receivers are communicably coupled to the surface of the medium respectively at the zone corner locations. Each receiver is responsive to the reception of an acoustic emission to provide a corresponding electrical output. The electrical response of the respective receivers are coupled to corresponding counters in a manner to enable the counters to sequence through their respective counting states. The receiver outputs are monitored to identify the first zone exhibiting an acoustic reception at all four corners. Once such a zone has been identified, all counters are inhibited from sequencing and are locked into the last counting state cycled.

Abstract: An elevator system including an elevator car mounted for movement in a building to serve the floors therein, and a car position indicator for indicating the position of the elevator car relative to the floors. A universal binary advanced car position signal is the input for a read-only memory programmed to output signals which drive the display portion of the position indicator to provide the notations desired for the specific building configuration. The power supply for the car position indicator intermittently activates the read-only memory to reduce the average power consumption thereof.