Build this DIY multi-zone transistor alarm using cheap off-the-shelf discrete components.
This is a photograph of the main circuit board of the Transistor Based Burglar Alarm. It features automatic Exit and Entry delays - together with a timed Bell cut-off and Reset. It's designed to be used with the usual types of normally-closed input devices such as - magnetic-reed contacts - micro switches - foil tape - and PIRs.
The basic alarm has two zone - one "Exit/Entry" and one "Instant". This will be adequate in many situations. However - larger buildings are best divided into zones. The modular design means that it's easy to Add Any Number Of Zones to the system. They are "Instant" zones - and may be triggered by both normally-open and normally-closed input devices.
Main Circuit Board
Four-Zone Expansion Module
You can Add Any Number Of Zones to the system. This is the circuit board of a Four-Zone Expansion Module. It's designed to be used with all the usual types of normally-open and normally-closed input devices such as - pressure mats, magnetic-reed contacts - micro switches - foil tape - and PIRs.
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