Abstract: 1. A reflectance modulator exhibiting an omni-azimuttal reflectance pattern comprising a microwave lens for focusing electromagnetic energy, a plurality of reflector means positioned on a focal surface of said lens and including a gaseous plasma, means for sequentially controlling the ionization level of said plasma to modulate the reflectance of said energy.

Abstract: A communication system apparatus and method for increasing the number of users accommodated by one or more communication channels. Time sharing of the one or more communication channels by a plurality of separate groups of users is provided as a function of user access demand, and channel occupancy. The one or more communication channels are periodically sampled by the user apparatus for detection of signals present on the channels whereby the occupancy status of each one of the scanned channels is determined. Transmission of signals from the user apparatus on each individual one of the channels detected as occupied by other users, is prevented for a predetermined length of time after each said detection of occupancy. Transmission of signals from the user apparatus is permitted on the channels detected as clear or unoccupied. The apparatus additionally provides for detection of each channel having signals addressed to the user and for transmission of reply signals from the user on the detected channel.