The GRI 4110 Series is basically a "vane" switch for use on storage units with overhead doors and latch type locks. Intended to be mounted on a roll up type door channel, the 4110 will not allow the alarms system to arm unless the bolt or latch, which serves as a "shunt" between the reed switch and magnet, is in a locked position. Removal or tampering of the bolt or latch removes the shunting effect and an alarm will be activated when the circuit is opened.