Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
129 words
A security alarm system comprising a control module (21) and at least one sensor (1) at a , location remote from the control module and cable-connected thereto, wherein the sensor (1) has a piezo-electric crystal (2) which, above a pre-settable limit of vibration, generates an alarm signal that is transmitted to the control module (21) and indicated at the sensor, such indication (15) being latched on after vibrations have ceased or decayed, and wherein the control module (21) has alarm means (24; 29) responsive to the alarm signal, characterised in that for setting up the system timing means (32) in the control module are switchable into circuit to transmit a periodic signal to the sensor which primes the sensor to its pre-vibrated state, removing any local indication of vibration.
Claim 2
Dependent Claim
129 words
A security alarm system comprising a control module (21) and at least one sensor (1) at a , location remote from the control module and cable-connected thereto, wherein the sensor (1) has a piezo-electric crystal (2) which, above a pre-settable limit of vibration, generates an alarm signal that is transmitted to the control module (21) and indicated at the sensor, such indication (15) being latched on after vibrations have ceased or decayed, and wherein the control module (21) has alarm means (24; 29) responsive to the alarm signal, characterised in that for setting up the system timing means (32) in the control module are switchable into circuit to transmit a periodic signal to the sensor which primes the sensor to its pre-vibrated state, removing any local indication of vibration.
Claim 3
Dependent Claim
26 words
A system as claimed in claim 1, characterised in that when the timing means (32) are in circuit, the alarm means (24, 29) are rendered inoperative.
Claim 4
Dependent Claim
45 words
A system as claimed in claim 1 or 2, characterised in that the periodic signal is a power supply for the sensor, the sensor being primed when the power supply resumes after an interruption, and then being settable by reference to its local indication (15).
Claim 5
Dependent Claim
29 words
A system as claimed in claim 1, 2 or 3, characterised in that the sensor has a SCR (13) which is latched on by a vibration above said limit.
Claim 6
Independent Claim
23 words
A system as claimed in any preceding claim, characterised in that the local indication at the sensor is provided by a LED (15).
Claim 7
Independent Claim
61 words
A system as claimed in any preceding claim, characterised in that the power supply to the sensor is via two pairs of wires coupled to form two loops out and back from the control module, one for supply voltage and the other for neutral, and wherein the alarm means (24, 37) is responsive to interruption of either loop at any point.
Claim 8
Dependent Claim
39 words
A system as claimed in claim 6, characterised in that the sensor has a removable cover and includes a switch (20) arranged to open one of said loops when that cover is removed, thereby to actuate an alarm (37).
Claim 9
Dependent Claim
21 words
A system as claimed in claim 6 or 7, including a plurality of sensors (1) connected in parallel across said loops.
Claim 10
Independent Claim
32 words
A system as claimed in any preceding claim, characterised in that the alarm means (24, 29) are arranged to be actuated on the occurrence of a short circuit in the cable connection.