ALARM SYSTEM

• Main Author: WINGER W,US
• Format: Patent
• Language: English
• Published: 14.05.1974
• Subjects: ALARM SYSTEMS; ORDER TELEGRAPHS; PHYSICS; SIGNALLING; SIGNALLING OR CALLING SYSTEMS

An alarm system includes two separate electrical loop circuits and means, such as diodes, controlling the supply of electrical power to the circuits so that normally one of the circuits is energized during one part of a given time period, e.g. the positive half cycle of an alternating current source common to the two circuits, and the other of the circuits is energized during the other part of such time period, e.g. the negative half cycle of such alternating current source. Alarm-condition sensors and associated normally-open switch means provide interconnection between the two circuits in case of an alarm condition so that current flows in one of the circuits from the other during the time such one circuit is unenergized. Such one circuit has a by-pass circuit portion containing alarm means and also has means for blocking normal current flow but not current flow from the other circuit, whereby the latter current flow activates the alarm means. Means may be provided in each circuit to indicate whether or not one of the other of the circuits becomes opened or shorted. A third circuit may be provided as a ground check.