Abstract: A power saving method and apparatus in a time division multiplexed system (10) capable of providing a synchronous full duplex communication between a telephone network (12) and a plurality of remote communication units (18). A communication resource controller (14) provides system synchronization, by periodically trnsmitting synchronization messages through one or more remote sites (11). The communication units (18) attempt to acquire synchronization during a synchronization acquisition interval. If synchronization is acquired, the communication units (18) enter a synchronous battery saving mode (515). In the synchronous battery saving mode (515), the communication units (18) can detect a call request either to their own address or to the address of another communication unit. If no call request is detected, the communication units (18) reduce power consumption for a synchronous power saving time interval, and thereafter merely verify synchronization.

Abstract: An improved quasi-duplex time division multiplexed (TDM) communication system provides for transmission by a talker until an interrupt command for role reversal is transmitted by a listener. Preferably, the time allocated for voice transmission is greater than the time allocated for command transmission. In this manner, the primary feature of full-duplex communications is provided simply while conserving spectrum.

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 semi-duplex communication system provides high channel efficiency by having the base station transmit a reference signal which each terminal uses as a sync signal. Each unit having data to send to the base responds with a very brief signal such as a burst of silent carrier transmission during an assigned time slot in a queue of slots. Only those units which responded thus are polled during the subsequent polling cycle. During the transmission time slots, the base can be sending acknowledgments to those terminal units having sent messages during the previous polling cycle. While polling for data or acknowledgments or sending acknowledgments, the base can also be listening for the respective responses. The address code of a terminal unit is further encoded to carry other required information in both directions.

Abstract: A pager or other selectively-addressed electronic device powered by a small power cell operates in four different modes and at two power levels, depending on signals received and a timing sequence. The device can stay active continuously, be activated at intervals or remain in a powered-down state. The address code assigned to a particular device would be transmitted at a predetermined time interval following a sync signal, thus the device can be powered-down until the approximate time period in which its address code could be transmitted. The system provides increased channel efficiency since information codes are superimposed on actual address codes, and there is no dead time in a channel while there are address codes waiting to be transmitted. The system is particularly well adapted to time multiplexing.

Abstract: Channel efficiency in a communications link between a controller and multiple portable units is increased by polling the active units and a set number of inactive units in a sequence where a "poll" consists of sending the binary coded address of the portable unit. The stream of transmitted data bits is only interrupted by a response from the portable unit, then resumed at the end of the response or a given portion of the response. During the reception of the response, certain other types of messages can be sent out by the controller. Portable responses can be automatic responses as to status, etc., or can be data initiated by the operator of the portable unit keyboard and stored in the portable unit memory until "armed" by the operator, then automatically transmitted to the controller when the portable unit address is received.

Abstract: A two-way communications system for use with a host computer includes a control unit, a base station and multiple radio/data terminal units. The control unit interfaces directly with the computer but uses a radio link to the portable units. Voice and data signals can be transmitted and data between units is decoded, sorted, stored, encoded, and sent to its destination in accordance with predetermined protocol in queue discipline. An extensive self-diagnostic system is included. An active redundancy arrangement switches between two control units/base stations on a regular schedule if both units are up, and instantaneously if the "on" unit goes down.