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US 4,754,262 AGranted
Multiplexed alarm system
AssigneeInteractive Technologies, Inc.
InventorsKenneth R. Hackett, Alan R. Permut
Life of this patent
Estimating the term…
Abstract
A multiplexing method for an alarm system is disclosed in which a plurality of transponders connected in parallel by a pair of wires each monitors an opening and responds to a synchronizing signal after a preprogrammed time delay corresponding to the particular transponder if the opening it is monitoring is secured.
Claims24
A multiplexed alarm system for monitoring a plurality of openings comprising:
- a plurality of contact means each connected with one of said openings, for indicating whether its respective opening is open or secured;
- a zone containing a plurality of transponders connected in parallel by a pair of wires, each transponder being connected with one of said contact means and including:
- means for receiving a synchronizing tone signal over said pair or wires;
- a bandpass filter for said tone signal;
- a synchronizing signal decoder responsive to tone signals from said bandpass filter;
- a precision oscillator;
- a programmable counter coupled to said oscillator and said decoder to count oscillations from said oscillator upon receipt of a decoded synchronizing signal;
- means for selectively programming said counter to produce an output at a predetermined count;
- means for generating an acknowledgment signal within a time slot after receiving said output of said counter;
- a current driver connected to said acknowledgment signal generating means for sending an acknowledgment signal on said pair of wires, said current driver having a high impedance to help minimize the loading on said pair of wires by said plurality of transponders;
- and
- means for preventing an acknowledgment signal from being sent if the contact connected to the transponder indicates that an opening is open;
- control means including means for sending said tone synchronizing signal to said zone of transponders and low impedance means connected to said pair of wires for receiving acknowledgment signals from said zone, said control means including means for causing an alarm if an acknowledgment signal is not received within the time slot corresponding to a particular transponder in said zone;
- and
- display means connected with said control means for providing an identification of the transponder(s) which caused an alarm.
12 more elements
A multiplexed alarm system for monitoring a plurality of openings comprising:
- a plurality of contact means each connected with one of said openings, for indicating whether its respective opening is open or secured;
- a plurality of zones, each containing a plurality of transponders connected in parallel by a pair of wires, each transponder being connected with one of said contact means and including:
- means for receiving a synchronizing tone signal over said pair of wires;
- a precision oscillator;
- a programmable counter coupled to said oscillator;
- means responsive to receipt of said synchronizing tone signal for initiating a count in said counter;
- means for selectively programming said counter to produce an output at a predetermined count;
- means for generating an acknowledgment signal within a time slot corresponding to the predetermined count of a particular transponder following the receipt of a synchronizing signal;
- a current driver connected to said acknowledgment signal generating means for sending an acknowledgment signal on said pair of wires, said current driver having a high impedance to help minimize the loading on said pair of wires by said plurality of transponders;
- and
- means for preventing an acknowledgment signal from being sent if the contact connected to the transponder indicates that an opening is open;
- control means including means for sending a synchronizing signal to each of said zones of transponders and low impedance means connected to the pair of wires in each of said zones for receiving acknowledgment signals from each of said zones, said control means including means for causing an alarm if an acknowledgment signal is not received within the time slot corresponding to a particular transponder in one of said zones;
- and
- display means connected with said control means for providing an identification of the transponder(s) which caused an alarm.
11 more elements
A multiplexing method for wired alarm systems comprising:
- sending a synchronizing tone signal;
- receiving said synchronizing tone signal in a plurality of transponders wired in parallel each connected to one of a plurality of contacts which indicate whether an opening is open or secured;
- counting a precision frequency in each of said transponders from the receipt of said synchronizing signal up to a preprogrammed count corresponding to the particular transponder;
- storing a high signal in a transponder if its respective contact indicates an opening that is open;
- resetting the high signal to a low signal at the end of a time slot following the completion of the preprogrammed count corresponding to the particular transponder if its respective contact is then secured;
- each of said transponders sending an acknowledgment signal upon completion of the preprogrammed count if it has a low signal stored;
- and
- causing an alarm if a transponder fails to send an acknowledgment signal at its preprogrammed count.
5 more elements
A multiplexed alarm system for monitoring a plurality of openings comprising:
- a plurality of contact means each connected with one of said openings, for indicating whether its respective opening is open or secured;
- a zone containing a plurality of transponders connected in parallel by a pair of wires, each transponder being connected with one of said contact means and including:
- means for receiving a synchronizing tone signal over said pair of wires;
- a bandpass filter for said tone signals;
- a synchronizing signal decoder responsive to tone signals from said bandpass filter and including means for indicating receipt of a troubleshooting synchronizing signal;
- a precision oscillator;
- a programmable counter coupled to said oscillator and said decoder to count oscillations from said oscillator upon receipt of a decoded synchronizing signal;
- means for selectively programming said counter to produce an output at a predetermined count;
- means for sending an acknowledgment signal on said pair of wires within a time slot after receiving said output of said counter;
- and
- means for preventing an acknowledgment signal from being sent if the contact connected to the transponder indicates that an opening is open unless said signal decoder indicates receipt of a troubleshooting synchronizing signal;
- control means for sending said tone synchronizing signal to said zone of transponders and for receiving acknowledgment signals from said zone, said control means including means for causing an alarm if an acknowledgment signal is not received within the time slot corresponding to a particular transponder in said zone, said control means further including means for sending a troubleshooting synchronizing signal;
- and
- display means connected with said control means for providing an identification of the transponder(s) which caused an alarm.
11 more elements
A multiplexed alarm system for monitoring a plurality of openings comprising:
- a plurality of contact means each connected with one of said openings, for indicating whether its respective opening is open or secured;
- a zone containing a plurality of transponders connected in parallel by a pair of wires, each transponder being connected with one of said contact means and including:
- means for receiving a synchronizing tone signal over said pair of wires;
- a bandpass filter for said tone signal;
- a synchronizing signal decoder responsive to tone tone signals from said bandpass filter;
- a precision oscillator;
- a programmable counter coupled to said oscillator and said decoder to count oscillations from said oscillator upon receipt of a decoded synchronizing signal;
- means for selectively programming said counter to produce an output at a predetermined count;
- means for sending an acknowledgment signal on said pair of wires within a time slot after receiving said output of said counter;
- latch means for storing a high signal if the contact connected to said transponder is opened;
- means for resetting said latch means after the time slot corresponding to said transponder if the contact connected to said transponder has been closed;
- and
- means for preventing an acknowledgment signal from begin sent if said latch means is storing a high signal;
- control means for sending said tone synchronizing signal to said zone of transponders and for receiving acknowledgment signals from said zone, said control means including means for causing an alarm if an acknowledgment signal is not received within the time slot corresponding to a particular transponder in said zone;
- and
- display means connected with said control means for providing an identification of the transponder(s) which caused an alarm.
13 more elements
Dependencies are inferred from the claim text.