Abstract: A data collection system in which, in communications between each of terminal units and a data collector through a power line, the data collector subjects a polling signal generated by a polling generating circuit to spread spectrum modulation by a spreading section, and superimposes the spread signal on the power line, while each of the terminal units subjects the incoming spread signal thereto superimposed on the power line to de-spread spectrum demodulation and recognizes it, and superimposes the data subjected to spread spectrum modulation on the power line after a certain period of time different from that in other terminal unit has passed. The data collector collects the data obtained by subjecting spread signals successively coming thereinto each by being superimposed on the power line to de-spread spectrum demodulation according to the polling.

Abstract: A diversity selection process for a wireless terminal having two antennas is disclosed which tests reception on both the main antenna and a diversity antenna during the period when the terminal is transmitting and tests reception of a different channel (for example, for mobile assisted hand-off) during an idle period when the terminal is neither receiving or transmitting data. The antenna with the greater signal strength is selected for the next frame. Thus, both diversity and mobile assisted hand-off measurements can be made with a single receiver.

Abstract: A multiplex device is provided for monitoring computer video signals and receives as input the video signals of a plurality of computers. The multiplex device selects the video signals of one of the plurality of computers to be inputted into a monitor for monitoring. The multiplex device for monitoring the computer video signals has three sets of switch circuits, a control signal generating circuit, three sets of voltage amplifying circuits, three sets of current amplifying circuits, a synchronous signal multiplex selecting circuit, and an interface circuit.

Abstract: A radio communication system adapting TDD/FH, for reducing interference of jammer, preventing third party's hearing, and enhancing frequency usage efficiency.