Electronic alarm circuit
OwnerGilbert Guillemotinventor
Life of this patent
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Abstract
An electronic alarm circuit for operating an audible alarm, such as a bell, has a trigger circuit arranged to continuously activate the alarm if a sensor is activated. The circuit also includes a capacitor arranged to be discharged if a normally closed test switch is opened. Closure of the test switch recharges the capacitor and renders the trigger circuit conductive. The alarm is thus activated but only for a restricted period dependent upon the time constant of the capacitor. Accordingly, it is possible to distinguish between a real alarm and the sound of the alarm when the circuit is tested.
Claims9
An electric alarm circuit comprising an alarm indicating section with an electromagnet having a movable armature and a normally closed contact, movement of the armature being arranged to operate an alarm, a sensor circuit comprising at least one switch alarm means, a capacitor and a resistor, and a trigger circuit causing the electromagnet to move the armature when the capacitor is charging, and connected in series with the normally closed contact, said capacitor being connected at the input of the trigger circuit through a normally closed test switch means located close said alarm indicating section, such that charging of the capacitor causes the trigger circuit to briefly conduct and energize the electromagnet thereby moving the armature, the movement of the armature causing the trigger circuit to become non conductive when said test switch means has been activated, whereby a single opening and closing movement of the armature is produced when said switch alarm means is not activated.
Dependencies are inferred from the claim text.