304UM0001 Rev 00
PD160 Enhanced Series User Manual
Page: 18 of 39
3.2.7.1
Power fail
The powerfail setting may be toggled on and off via this selection in
the reset menu. Off by default, this setting is designed to retain the
memory of a vehicle on the loop in the event of a power fail situation.
This is designed specifically for fail-safe situations to retain the output
state and prevent a glitch on the outputs for a power failure. As such,
when the power is restored, the detector will not retune but return to
the detect state prior to the power failure. If a vehicle was on the loop
during the power failure, it will remain detected when the power is
restored. Thus it prevents the tuning out of a vehicle over the loop
during a power failure condition.
The memory retention of the vehicle is designed to be infinite, but is subject to the following limitations:
The level of the detect must be sufficiently greater (at least 0.5%) than the sensitivity level or
else the maximum potential temperature drift from one time of day when the power fails to
another when the power returns mustn’t exceed 20°C.
The level of the detect should be no less than 0.15% and a minimum of 0.15% above the
sensitivity level.
If the presence of a vehicle should occur less than a second before power is lost, there is a
chance that the unit won’t retain the detect and the outputs could toggle on restoration of
power.
If these conditions are not met, it is possible for the detect condition to be lost on recovery of power.
If Powerfail is used in conjunction with AFS and there is a concern of a channel going into fault, use
AFS to select the best band and then turn it off to prevent the unit retuning on recovery.
