Abstract: A method and apparatus for detecting objects disposed in close proximity to a conductive loop, includes the use of a sensitivity selection circuit to compensate for loop sensitivity to metal and other conditions, and a microprocessor circuit for helping to prevent false detections or undesired interruptions of valid detection due to changes in environmental conditions.

Abstract: A light frequency communications system and method of using the system is disclosed. The system includes a base station and a plurality of remote units wherein the base station and all the remote units communicate in a full duplex mode utilizing a single light wave carrier. Multiplexing between the units is accomplished by modulating an audio signal on at least one subcarrier frequency.

Abstract: A stationary optical antenna forming a part of a full duplex optical communication system, includes optical emitter and receptor devices having peak power axes, and a mounting arrangement for positioning the devices at an elevated location within a room with their axes directed downwardly at a given angle to a horizontal plane, based upon the height of the devices above the floor, thereby enabling remote portable transceivers to be able to communicate therewith within the same room. Baffles help prevent interference between the emitters and receptors, and a compensation circuit is employed to enable the optical communication to take place, even in bright light conditions.

Abstract: A wireless communication system is adapted to be used as an intercom system in a multiple customer station configuration. A customer service representative portable transceiver communicates wirelessly with a stationary base station to enable the representative to move freely about, and thus be able to perform other tasks. The base station is connected electrically to a group of substantially similar physically spaced apart remote customer drive up stations. Each of the remote stations includes a call initiating device for enabling a customer at a drive up station to request communications with the representative. The base station includes a signal generator, which responds to a call initiating device requesting a communication link. A transmitter responds to the generator to send an attention attracting signal to the representative's transceiver, so that the representative can cause the establishment of an audio communication link to a selected customer station.

Abstract: A battery charging system which prevents false switching from a fast charge mode to a trickle charge mode due to low frequency voltage aberration signals. The battery charging system includes a battery voltage analyzer and a plurality of battery charging and conditioning units for charging different types and kinds of nickel cadmium batteries. Firmware in the microprocessor rejects low frequency aberrations permitting a desired voltage signal to be produced which is indicative of the actual battery potential for charge switching purposes.

Abstract: A wireless optical short-range communication system adapted for use as an intercom system. The system can be used in fast food restaurants and similar commercial institutions. The communication system includes a base station to interconnect via optical communication a group of substantially similar physically spaced-apart, remote units. Each one of the remote units and the base units includes an optical emitter to transmit an optical message-carrying beam to the base station, and an optical receptor to receive an optical message-carrying beam from the base station. The base station includes a receptor for receiving the optical beam transmitted by the optical emitters of all of the remote units, and an optical emitter to relay the received optical beam to the optical receptors of all the remote units.