Abstract: A two-way radio includes a receiver having a squelch circuit and a selective calling decoder. A transmitter is connected to an inhibit circuit. The inhibit circuit is responsive to the selective calling decoder for permitting transmission after reception of the radio's ID code. The inhibit circuit inhibits further transmissions if the squelch circuit indicates loss of carrier for more than a predetermined time during receive.

Abstract: A signalling and control protocol is provided wherein each subscriber unit (106) operating within a communication system (100) must transmit a request (200, 200' or 200") to communicate to a central station. If a communication channel is available, the central station returns a channel grant (210), which includes a time code representing a time duration during which the requesting subscriber may communicate. After receiving the channel grant (210), the subscriber unit may communicate for a time interval not exceeding the time duration, and, immediately prior to the expiration of the time duration, the subscriber unit may itself provide a warning tone indicating the impending loss of the communication channel. Conversely, if a communication channel is not available, the central station provides a busy message (216), which includes a code (218) representing the requesting subscriber unit's position is a call request queue.

Abstract: A radio communication system includes a base station and a plurality of remote units. The remote units can be operated in one of several modes. In the Message Storage mode, a telephone or remote unit caller is verbally informed that the called remote unit is not receiving calls, and the caller is then given the option to store a voice or numeric message for later transmission to the called remote unit. If a caller enters an Override code, however, the system attempts to establish voice communication between the caller and the called remote unit. In the Call Screening mode, the caller's message is stored in the base station and, simultaneously, forwarded to the called remote unit. During reception of the message, the called remote unit can "pickup" the call and begin normal voice communications with the caller. When a remote unit changes from the Message Storage mode to some other mode, its stored messages are automatically forwarded to the remote unit.

Abstract: A low profile antenna structure includes a substantially planar conductive sheet having a substantially planar conductive member extending from one end at a normal angle. A driven radiating element and a parasitic radiating element are disposed adjacent the conductive sheet. A feed point is coupled to the driven element for coupling RF energy to and from the antenna. Both the driven and the parasitic elements are approximately one quarter wavelength long and are approximately parallel to one another and are situated approximately 1/20th of a wavelength apart.