Re: End Of Line Terminating Resistor, Or Module, On Older Interconnected Smoke Detectors ?

[rwies@xxxxxxxx]

Most system type smoke detectors require an end of line resistor.  4 wire
smoke detectors require an end of line power supervision relay.

The end of line supervision relay power wires connect to the smoke detector
power at the last smoke detector (end of line).  The contact set that is
closed when energized is connected across the fire alarm detection loop with
the resistor in series with the relay.

This way, when the smoke loop has power the resistor is connected across the
end of the smoke loop.  If a smoke detector goes into alarm it will short
across the detection loop and the control panel will see this as an alarm
condition.  If the smoke loop loses power, the relay will open and thus
remove the resistor from the end of the line.  The control panel will see
this as a fire trouble.

I have been in the industry for about 36 years and this is how they were
when I started.  There may be some older systems that operate differently.

Best of luck,

Ron Wies