Abstract: A monitoring system and method for a radio communication apparatus, including a base station and a plurality of portable units, for monitoring a state of each of the portable units. The base station transmits a first asking signal to each of the portable units at each occurrence of a first predetermined time period. Each portable units replys to the first asking signal only when a state of the portable units becomes abnormal. The base station also transmits a second asking signal to each of the portable units at each occurrence of a second predetermined time period. Each portable units replys to the second asking signal to indicate an operation state of the portable unit.

Abstract: In a digital radio communications system, a mobile station in the service zone of a first base station transmits a reconnect request packet to a second base station when leaving the service zone of the first and entering the service zone of the second during a session with the first base station. The second base station communicates the receipt of the reconnect request packet to the central station, from which a proceed-to-clear command packet is sent to the first base station to allow it clear the connection with the mobile station and return a clear response packet to the central station informing it of a serial number of the last data packet it has received from the mobile station immediately before leaving its service zone. On receiving the clear response packet, the central station sends a reconnect command packet indicating that serial number to the second base station to cause it to issue a reconnect response packet to the mobile station requesting the reconnect.

Abstract: In a radio concentrator system, a master station and a terminal station cooperate with each other to establish connections between remote subscriber terminals and a public switched network through radio message channels. An intraoffice call is set up between first and second subscriber terminals through the connections established in the terminal and master stations via the network. Upon establishment of such an intraoffice call, the terminal and master stations clear their connections and reestablish local connections in the terminal station between the subscriber terminals. The master station transmits a polling signal at periodic intervals to the terminal stations, which responds to it by transmitting an acknowledgement signal as long as the local call is in progress. The master station detects if the acknowledgement signal is received in response to the polling signal.

Abstract: In a communication network comprising a base station and a plurality of substations communicable with the base station through radio channels including a control channel, at least one of the substations comprises a memory unit (31) for storing an identification signal representative of an off-hook subscriber when no idle channel is found out in the radio channels. When an idle channel is detected by an idle channel detector (24), the identification signal is read out of the memory circuit to be sent to an idle channel notification circuit (32). The idle channel notification circuit automatically informs the off-hook subscriber of occurrence of the idle channel through a subscriber interface circuit (16) by the use of a specific ringing signal. Alternatively, the identification signal may be sent from the substation to the base station and returned back to the substation so as to avoid collision among off-hook subscribers.

Abstract: There is disclosed a circuit for monitoring a capacity of a subscriber line to which a capacitor equivalently representative of a telephone set is connected. This monitoring circuit has a test sequence for the subscriber line capacity. The test sequence comprises a first step to connect the subscriber line to a test circuit, and second step to apply a backward voltage to the subscriber line, thereby to discharge an electric charge stored in the equivalent capacitor. The test sequence further comprises a third step to apply a forward voltage to the subscriber line through a reference capacitor, thereby to charge the equivalent capacitor to evaluate the capacity value of the equivalent capacitor on the basis of a voltage appearing across the equivalent capacitor, thus to effect a capacitive test of the subscriber line.