Abstract: A transmitter for transmitting an intermittent sequence of messages to maintain synchronization between the transmitter and a receiver. The transmitter includes control apparatus which provides messages for transmission, each message forms part of a sequence of messages and includes control information and timing information, and transmission apparatus which transmits each message. A receiver for synchronizing with a sequence of the transmitted messages. The receiver includes receiver and synchronization apparatus responsive, when enabled, to the control information in the message to indicate to the control apparatus reception of the message. The control apparatus controls power conservation by disabling the receiver and synchronization apparatus for a period of time dependent upon the timing information and enabling the receiver and synchronization apparatus to receive a following message in the sequence.

Abstract: A transmitter, for controlling at least one receiver by intermittently transmitting groups of messages. The transmitter includes a controller arranged to provide intermittently groups of messages for transmission. Each of said groups includes a plurality of messages in series and separated by time intervals, wherein each of the plurality of messages in a group includes control information such that control of the receiver can be effected by reception of any one of the plurality of messages in the group. The invention increases the efficiency with which control messages can be transmitted without markedly increasing the power consumption of transceivers in a radio frequency network.

Abstract: An improved paging procedure for use in a low power radio communications network. A transceiver which pages a device by periodically transmitting a series of messages, comprises a transmitter which transmits a series of messages comprising a message at each frequency in a predetermined series of frequencies, a receiver which receives at, at least a predetermined frequency; and a controller which enables the transmitter and then the receiver in each of a plurality of successive periods and provides each message in said series of messages. The predetermined series of frequencies is an ordered series. A first message in the series of messages transmitted in a period defines directly or indirectly when the receiver is enabled and a second message in the series, a mark code, directly defines the predetermined frequency.

Abstract: The description covers the identification of the position of data packets (P1, P2, . . . ) which are located in a serial received data stream and each have check data in a check field and a check sum (CRC) which is formed using the check data, the received data stream being passed in serial form through at least one comparison unit (9) which forms a new check sum (CRC′) with each received signal to be newly added and compares this new check sum with data which are looked at for the associated received check sum (CRC), and, furthermore, during the comparison, the influence of all data is eliminated which do not belong to the check data and to the check sum (CRC).