DSP-22-1 User Manual
Page 8 of 22
DSP-22-1_MAN_D
without having to be overly sensitive and susceptible to false detections. NOTE: If detection of high-bed tractor-
trailers is required, correctly sized loops must be used.
DIP
Switch 3
Function
OFF
Channel 1 Normal Sensitivity
ON
Channel 1 Sensitivity Boost
Channel 1
–
Frequency (S3 DIP Switches 1 and 2)
When loops are installed sufficiently far apart, any two loops will not interfere with each other. However, if two
loops are fairly close together, say two to four feet apart, the inductive fields may couple together and may
interact causing intermittent false detections. The main variables for inductive coupling are loop size, distance
between loops, and the loop frequency. Loops that are connected to the same DSP-22-2 detector can not interfere
with each other, as the detector will only turn on one of the loops at any point in time (this is referred to as
scanning). To aid in mitigating inductive coupling, each DSP-22-2 unit comes with two frequency switches for each
channel. They are binary coded allowing up to four different operating frequencies.
If there are suspicions that loops are interacting, change one of the detector’s frequency settings for the suspect
channel so that their inherent frequencies are sufficiently different as to no longer interact. If the loops are the
same size and number of turns, setting one channel to high and the other channel to low will provide the maximum
frequency separation.
DIP Switch
Frequency
1
2
OFF
OFF
Channel 1 High
OFF
ON
Channel 1 Medium High
ON
OFF
Channel 1 Medium Low
ON
ON
Channel 1 Low
Channel 1
–
Presence / Pulse (DIP Switch 4)
The operating mode for channel 1 is selected with DIP switch 4 (Presence or Pulse) and affected by the setting of
DIP switch 5 (Loop or Probe). Presence detection for channel 1 is only available in the inductive loop mode of
operation (DIP switch 5 OFF). If channel 1 is in the probe mode of operation only pulse on entry operation is
available regardless of the setting of DIP switch 4.
In the Presence mode of operation, once activated, the output will remain activated for as long as a vehicle is
detected over the loop. After four minutes of continuous detection, the detector will begin a proprietary
algorithm that is designed to be able to reliably detect the vehicle for long periods of time (days or even weeks)
while still being able to drop the detection once the vehicle exits the loop.
When the probe mode of operation is selected (DIP switch 5 ON), pulse on entry is the only detection mode of
operation for Channel 1. If DIP switch 5 is OFF and DIP switch 4 is ON, Channel 1 is in the pulse mode.
