| 摘要 |
A pressure switch comprises a plastic housing (1) wherein there is moulded a reed relay (2). Beside the reed relay (2) there is provided in a recess in the switch housing (1) a permanent magnet (3). A movable switch arm (4) pivots about a shaft (5) mounted in the switch housing (1) and is raised by means of a spring (6) which also locks the shaft (5). When the switch, against the spring force, is in abutment with the switch housing (1), a downwardly projecting lug (10) on the side of the switch arm (4) forms a shield which shields the reed relay (2) from the magnetic field of the magnet (3). In this position of the switch arm (4) the switch is open, and is closed if the switch arm is raised by a certain angle by means of the spring (4). A pressure switch of this kind is particularly suited as an armoured or alarm switch in cars, but can also form part of a series of several other such switches in an alarm circuit. In this case it is advantageous to provide a resistor (R) in parallel over the reed relay and similarly in the switch housing (1). Such switches can be used in both car alarms and house alarms.
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