Alarm system

Claim 1

In an alarm system utilizing a bidirectional CATV system for remotely monitoring a plurality of subscribers of said CATV system from a central station connected to said CATV system, the improvement comprising: (a) a plurality of subscribers stations each located at each subscriber's location and having locations in group units; (b) a plurality of tone generators each provided in the corresponding one of said subscriber stations, said tone generators generating up-signals of first frequencies common to respective of said group units, said first frequencies being different for respective subscribers in respective group units; (c) means disposed in said central station for sequentially generating a plurality of first signal components of different frequency components respectively corresponding to a plurality of types of alarm contents, said plurality of first signal components being periodically generated repeatedly, the frequencies of said first signal components being different from said first frequencies of said up-signals; (d) means disposed in said central station for generating a plurality of second signal components of different frequency components respectively corresponding to said plurality of group units, said plurality of second signal components being periodically generated repeatedly, the frequencies of said second signal components being different from the first frequencies of said up-signals and the frequencies of said first signal components; (e) synchronizing means disposed in said central station for controlling the duration time of each signal component and the repetition period of said first and second signal components in such a manner that one cycle of repetition of one of said first and second signal components is completed within the duration time of each signal component of the other of said first and second signal components; (f) means for delivering said first and second signal components as interrogating signals from said central station to a transmission cable of said CATV system; (g) repeater means disposed in said transmission cable and including means for branching and transmitting the first signal components in said interrogating signals to each of said group units; (h) a plurality of alarm switch means disposed in each of said subscriber stations and connected to said tone generator therein, whereby when an abnormal condition occurs in the location of each said subscriber station, one of said alarm switch means corresponding to the said abnormal condition is actuated; (i) discriminating means disposed in each said subscriber station for receiving, separating and detecting the respective frequency components of said first signal components; (j) controlling means disposed in each said subscriber station whereby in response to the detection outputs of said discriminating means, operation and non-operation of said alarm switch means are sequentially polled so as to sequentially control the delivery of the outputs of said tone generator to said transmission cable through said alarm switch means as said up-signals; (k) means disposed in said repeater means for receiving said second signal components and separating the same into the respective frequency components to generate a plurality of detection signals; (l) means disposed in said repeater means for separately receiving said up-signals from said group units, whereby in response to said detection signals corresonding to the frequency components of said second signal components, said up-signals from said group units are sequentially transmitted group by group to said central station through said transmission cable in synchronism with the period of said second signal components; (m) means disposed in said central station for receiving said up-signals through said transmission cable to separate the same into said first frequencies and generate a plurality of detection outputs; (n) a plurality of AND gate means disposed in said central station for receiving in a matrix manner at the inputs thereof a plurality of first binary codes each having a signal content indicative of the presence or absence of corresponding one of said plurality of first signal components, a plurality of second binary code signals each having a signal content indicative of the presence or absence of corresponding one of said plurality of second signal components, and a plurality of third binary code signals each having a signal content indicative of the presence or absence of corresponding one of said plurality of detection outputs; and (o) a plurality of indicator means disposed in said central station, each of said indicator means being operable by an output of corresponding one of said plurality of AND gate means.