Wiring an external SAB bell

On an external bell to the SPC controller board the relay output is wired to the strobe input with Bell Hold Off (BHO) and Tamper Return (TR) connected to their respective inputs on the external bell interface.

A resistor (2K2) is pre-fitted on the controller board between the BHO and TR terminals. When wiring an external bell, connect this resistor in series from the TR terminal on the controller to the TR terminal on the external bell interface.

External bell wiring

Label	Description
A	Strobe +
B	Strobe –
C	Hold off
D	Tamper return
E	Bell -
F	Bell +