US 4,361,833 AGranted

Multi-sensor alarm system and method of protecting a premises

AssigneeMonitran International, Inc.

InventorRichard P. Allgood

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Abstract

A multi-sensor alarm system and method of protecting a premises include at least one sensor circuit and an alarm circuit which together establish a two-wire closed loop electrical circuit path in which a wide variety of alarm sensors are accommodated. The sensors include two-contact configurations which are normally-closed or normally-open, as well as multiple-contact configurations which are characterized by both normally-closed and normally-open contacts. Each sensor differently changes the electrical parameters of the circuit path; and the alarm circuit includes a transistor which senses each parameter change, and a timer which generates an alarm signal whenever any of the sensors is actuated. Opening or closing the circuit path at any point therein will cause the alarm signal to be generated. A status indicator constantly monitors and supervises the status of the sensors in the circuit path. An alarm indicator is latched to the ON-state to constantly indicate the fact that the alarm signal has been generated. A manual-reset switch returns the alarm indicator to its OFF-state. The alarm system reconditions itself such that more than one sensor can be tripped, no matter whether the particular sensor is of the non-resettable or of the automatically-resetting type.

Claims29

Dependent claims

A multi-sensor alarm system, comprising:

(a) electrical circuit means for establishing a two-wire closed loop circuit path having a load impedance through which an electrical current is conducted;
(b) first sensor means electrically connected in the two-wire closed loop circuit path for detecting an alarm event, said first sensor means being actuatable in response to detection of the alarm event from a non-alarm state in which the electrical current is conducted through the first sensor means, to an alarm state in which the electrical current is prevented from being conducted through the first sensor means;
(c) second sensor means electrically connected in the same two-wire closed loop circuit path for detecting the alarm event, said second sensor means being actuatable in response to detection of the alarm event from a non-alarm state in which the electrical current is prevented from being conducted through the second sensor means, to an alarm state in which the electrical current is conducted through the second sensor means;
(d) each of said sensor means being respectively operative to differently change the electrical characteristics of the two-wire closed loop circuit path in response to actuation of each sensor means between its respective states;
(e) alarm means electrically connected to the same two-wire closed loop circuit path, for sensing either differently changed electrical characteristic of the circuit path, and for generating an alarm signal when either of the sensor means is in its respective alarm state, said alarm means including a switching element actuatable among a fully-on switched condition, a fully-off switched condition, and an equilibrium condition intermediate the fully-on and fully-off switched conditions, and means for establishing the equilibrium condition when both sensor means are in their non-alarm states, and wherein each of said sensor means is operative to actuate the switching element away from its equilibrium condition when either sensor means is in its respective alarm state;
and
(f) supervisory means for constantly monitoring the status of the switching element and the sensor means, said supervisory means being operative to separately indicate when both sensor means are in their non-alarm states and said switching element is in its equilibrium condition, and to separately indicate when said first sensor means is in its respective alarm state and said switching element is in one of said switched conditions, and to separately indicate when said second sensor means is in its respective alarm state and said switching element is in the other of said switched conditions.

4 more elements

A method of protecting a premises, comprising the steps of:

(a) establishing a two-wire closed loop main circuit path about the premises;
(b) conducting an electrical current through the main circuit path;
(c) electrically connecting a first sensor means in the main circuit path for detecting an alarm event, said first sensor means being actuatable in response to detection of the alarm event from a non-alarm state in which the electrical current is conducted through the first sensor means, to an alarm state in which the electrical current is prevented from being conducted through the first sensor means;
(d) electrically connecting a second sensor means in the main circuit path for detecting the alarm event, said second sensor means being actuatable in response to detection of the alarm event from a non-alarm state in which the electrical current is prevented from being conducted through the second sensor means, to an alarm state in which the electrical current is conducted through the second sensor means;
(e) differently changing the electrical characteristics of the main circuit path by respective actuation of each sensor means between its respective states;
(f) sensing each differently changed electrical characteristic of the main circuit path, and generating an alarm signal when either of the sensor means is in its respective alarm state, said sensing step including the step of electrically connecting an actuatable switching element in the main circuit path, said alarm signal generating step including the step of establishing an equilibrium condition for the switching element which is intermediate its fully-on and fully-off switched conditions;
and
(g) separately indicating when both sensor means are in their non-alarm state and said switching element is in its equilibrium condition, when said first sensor means is in its respective alarm state and said switching element is in one of its switched conditions, and when said second sensor means is in its respective alarm state and said switching element is in the other of its switched conditions.

5 more elements

Dependencies are inferred from the claim text.