Security appts. for e.g. doors - has coding device operated by external knob to enable alarm to be cancelled by authorised user

摘要

The security and warning device for doors etc. consists of a housing in two parts (12,30) which is fixed by a one hole mounting to the inside of the door (10), and contains the supply source i.e. battery (36) and rotary switch (22). The switch (22) is constructed as a coding device with four contact strips and ten switch positions, so that the numerals 1 to 0 can be formed as four digit binary information. The underside of the housing has a hollow screwed shaft (13) which protrudes through the door (10) to the outer side where a flanged collar (15) is slipped over it and a locknut (16) screwed up, holding the inner housing tight against the inside of the door. A rod (14) inserted inside the screwed shaft (13) has an operating knob (17) fixed to the end outside the door, the inner end being part of a housing (19) which is connected to the switch code device (22), and turns the latter. A door contact protruding from the housing will trip the alarm if the door (10) is opened, but by inserting the right code via the operating knob (17), the user can open the door without actuating the alarm.