Laboratory 24/Alarm cabling

Overview

The sensors and cables still remain, but the original control unit has been removed. Te frame in which it sat is still present and affixed to the wall above the electrical distribution. All cable runs end up, somehow, at this location. The cable runs are all 8 core, though not all cores need be used on a given run.

The section names in this article match the legends written on the cables themselves.

Front Door + PTS

Blue/yellow

Door switches

NC circuit, impedance increases with one or both doors open

Impedance	Door state (viewed when inside, facing out)
open circuit	Wire cut/tamper
14k1	Both doors open
9k4	Indeterminate; either of L open, R closed L closed, R open
4k7	Both doors closed, i.e. the normal state
0R	tamper

Green/white

Push to secure (the switch on the outside of the front door. Originally this would have been used to signal that the last occupant had left and the building was properly secure)

NO circuit (at 4k7) , goes short when button pushed

Other pairs unused