Apparatus for signalling system

Abstract

Apparatus for a signalling system. The signalling system includes a remote control unit arranged to communicate with a centralized communications center. The remote control unit operates at or following a specified time of day to initiate a self-check call and to communicate data to the communications center. The communications center includes a disc unit which stores therein self-check timing data specifying the time of day at which the remote control unit is scheduled to initiate a self-check call. A computer at the communications center receives data from the remote control unit and operates in response thereto to update the self-check timing data in the disc unit to specify the time of day at which the next self-check call is to be initiated by the remote control unit. In the absence of data from the remote control unit, there is no updating of the self-check timing data. On a regular basis, the self-check timing data in the disc unit is compared with time-of-day data produced by a clock and representing the present time of day. In the event the self-check timing data in the disc unit specifies a time of day earlier by more than a predetermined amount than the present time of day, the computer operates to produce an output condition indicating a missing or late self-check call. The output conditions may be used in the preparation of a hard-copy printout for maintenance purposes.