4422181 Bi-directional fibre-optic coupler

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4422181

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BI-DIRECTIONAL FIBRE-OPTIC COUPLER

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David A Grafton, Eric B Hochberg, Ronald E Purkis assigned to The United States of America as represented by the Secretary of the Army ....... L

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conversations are established by single-span transmission between subscribers of the peripheral stations. In order to prevent conflicts arising from two simultaneous call demands, a rectangular-wave synchronization signal is transmitted by the central station to the peripheral stations in a specialized channel and the demands are caused to coincide with the active wavefronts of the synchronization signal.

A bi-directional fibre-optic coupler providing about 70 dB to about 100 dB isolation from near end transmitter radiation in a system that transmits signals in opposite directions over a single fibre and thereby provides a low-loss coupler having operational characteristics to handle reception and transmission with sufficiently low value of crosstalk,

4423413 RADIOCOMMUNICATION SYSTEM IN WHICH A RECEIVING STATION MONITORS A NUMBER OF TRANSMITTERS BY T I M E D I V I S I O N

4422178

Silva Herma da, Voorburg, Netherlands assigned to Staat der Nederlanden (Staatsbedrijf der Posterijen Telegrafie en Telefonie)

RADIO COMMUNICATION RECEIVER HAVING AN OSCILLATOR CIRCUIT OF LOWER POWER-CONSUMPTION

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Toshihiro Moil, Tokyo, Japan assigned to Nip-. pon Electric Co Ltd

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System for transmitting, via raulocommunication channels, call messages as specified in CCIR Recommendation 493-]. The transmitter transmits every call message, having a duration t, n

A radio paging receiver having two power sources, a receiver, a decoder and an oscillator, provides power from the lower of the two voltage sources to the oscillator when the paging receiver is turned off and provides power from the higher of the two voltage sources to the oscillator when the paging receiver is turned on. The oscillator provides higher power pulses to the decoder immediately upon the turn on of the pager thereby providing an immediate normal tone sound from the paging receiver.

times with a message frequency r. The receiving station, designed for monitoring calling stations by time division has a monitoring period T = ( n l)/(n+ l)*t/r per station to be monitored. Only one receiver is used. The identification signal of the called station will always be recognized during one of the monitoring periods T, after which the monitoring period can be prolonged, if necessary. III