Loop Detector

The LD-1123-PAQ Loop Detector is designed to be used with gates or other vehicle detection systems. The unit connected to an input loop which is buried in the pavement. If a vehicle is over the input loop, the detector sends a signal to perform such actions as opening a gate, holding a gate open, or indicating that a vehicle is in a bay.

  • Single loop input
  • 3 Adjustable sensitivity settings
  • 2 Form “C” relay outputs
  • 11-Pin connector
  • ABS plastic housing
  • Power-on automatic reset
  • Automatic drift compensation for varying environmental conditions
  • Auto fault detection
  • Weather-resistant (IP54)
  • Terminal block (LD-ACC-TB) included
Operating Voltage 12~24 VAC/VDC
Current Draw Standby: 40mA@12VDC / 40mA@24VDC
Active: 50mA@12VDC / 60mA@24VDC
Sensitivity High, Med, Low
Reaction time 100ms
Output relay Pulses relay #1 or #2 (default) on entry; selectable via DIP Switch #1*
Presence time Permanent (default) or 5min†; selectable via DIP Switch #2*
Delay time on exit No delay (default) or 2.5s; selectable via DIP Switch #3*
Loop frequency 20kHz or 170kHz (default); selectable via DIP Switch #4*
Loop induction range 80~300 μH
Fault output Relay #2‡ is continually energized and the green LED stays on
Pulse output time 200ms
LEDs Red: Power indicator
Green: Status indicator (vehicle detected or fault)
Input / Output protection Built-in surge and transient protection
IP Rating IP54
Case material Black ABS plastic
Operating Humidity Up to 95% without condensation
Operating Temperature -40°~149°F (-40°~65°C)
Dimensions 2-15/16″x1-7/16″x3-5/16″ (74x36x85 mm)
Weight 7.2-oz (203g)

*See DIP Switch Settings, pgs. 3~4 in the manual.
†5min presence output setting should only be selected if a secondary safety device is in use.
‡Depending on settings, see DIP Switch Settings, pgs. 3~4 in the manual.

Product Information Sheet (PI)


Sensor does not detect the vehicle
  • Make sure that unit is powered up (red LED is lit) and has completed the initial self-test
  • Adjust the sensitivity setting
  • Check for fault in the loop or loose connection to detector
Sensor’s green LED lights when vehicle is detected, but there is no output
  • Check wiring between the sensor and device to be triggered
Detector continues to detect even after a vehicle leaves the loop
  • Check for fault in the loop or loose connection to detector
Detector sometimes detects even when there is no vehicle over the loop
  • Check for fault in the loop or loose connection to detector
  • Check for cross-talk between adjacent loops – adjust frequency
  • Check whether the loop is being triggered by other metallic objects nearby – gates, metal doors, pavement reinforcement
  • Loop may not be securely installed in pavement to prevent movement or moisture intrusion
Green LED flashes quickly
  • Check for loop short circuit
  • Check for loose connection between the loop and detector
  • Ensure loop inductance does not exceed permitted range

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