Abstract: A portable communication device capable of operating in a telephony mode and in a dispatch mode is disclosed. The device includes a proximity sensor and a first speaker mounted on a front panel and a second speaker mounted on a rear panel. The operation of the speakers is controlled in accordance with the operational state of the device as well as the output of the proximity sensor.

Abstract: A multiple access communications system reuses a set of either N carrier frequencies or time slots in adjacent communications sites to provide more than N or T minimally cross-correlated frequency or time hopping communications channels respectively. A first set of communications channels is associated with a first of the communications sites. No two of the channels in the first set employ the same frequency or T time slots at the same time. A second set of communications channels is associated with a second of the adjacent communications sites. No two of the channels in the second set of channels employ the same one of the N carrier frequencies or T time slots at the same time. One or more sets of the minimally cross-correlated channels are further defined so that none of the channels in such sets employ the same frequency at the same time as more than a predetermined number of the channels in another of the sets of the minimally cross-correlated frequency-hopping communications channels.