Magnetically activated proximity switch for security alarm system - has reed switching element between reed contact and short circuit loop to suppress interference fields

摘要

The reed contact device uses a pair of contacts to monitor the closed condition of a door or window. The contacts are actuated by a magnet. An alarm contact pair (3) is located between the switching contacts and short circuit loop (2). Due to different response sensitivities of the reed contacts, the alarm contact will not close when the switch contacts are activated. Located between the two sets of contacts is pref. a magnetic screening element (4) that limits the effect of the switching magnet on the alarm contact. An alternative version uses two differently sized screening elements. ADVANTAGE - Reduces possibility of unauthorised manipulation.