Install End of
Line Resistance
End of line resistors (EOLR) are resistors of
a specified value that are used to terminate protective loops or zones.
The purpose of EOLR's is to allow the control panel to supervise the field
wiring for open or short circuit conditions. How the alarm responds to each
depends on the panel as well as system zone programming, but generally
speaking, an alarm views an open circuit as a fault or alarm condition, and a
short circuit as a trouble or alarm condition (if armed). The purpose of EOLR's
is to allow the panel to differentiate between the two conditions by looking
for a known resistance.
EOLR's should be installed at the last device on the loop, electrically
speaking, and not inside the control, unless special conditions are met. The
benefits of EOLR's on protective zones with all concealed wiring is commonly
argued by professional installers, as well as EOLR's installed inside the
control unit, negating their effectiveness, as well as disabling the EOLR
feature and using NC (normally closed) loops for zone definitions. The use of
EOLR's is recommended and is particularly important when the field wiring is
subject to damage or compromise.
Some equipment supports Double End of Line Resistors (DEOLR) to further
differentiate between conditions that may exist on the loop.