TD424NT Four Channel NEMA format Vehicle Detector

The TD424NT is a high performance, 4 channel, NEMA format, microprocessor based vehicle detector.
This purpose designed traffic detector has been developed for general-purpose vehicle monitoring and traffic control applications. This unit meets the criteria for AS2703-2008.


  • Configurable delay and extend timings allow customisation for specific applications.
  • Optimised sensitivity levels chosen for traffic control applications allowing adjacent lane rejection and elimination of adjacent lane interference.
  • Adjustable presence times for operation in passage mode, limited presence or for queue detection.
  • Mode selection to operate either as a Presence Detector or a Passage Detector.
  • Loop-fault monitoring with faceplate indications of loop faults on a per-channel basis.
  • Sequential polling techniques to positively eliminate crosstalk between loops.
  • Selectable options :
    1. “Anti – lock” for positive change rejection,
    2. “Auto-retune” to protect against faulty loops in multiple loop configurations.

Product codes

878FT0021- TD424NT (Relay) - 12-24V DC

878FT0037 - TD424NT (Opto) - 12-24V DC

Self tuning range: 20-1000µH
Sensitivity: Seven step adjustable on faceplate:
Step 7: 0.02% ΔL/L
Step 5 -6 : 0.05 / 0.1%Δ L/L
Step 2-4 : 0.2 / 0.3 / 0.4 % ΔL/L
Step 1 : 0.5% ΔL/L
Frequency: Four step adjustable on face plate,
20- 140kHz (frequency determined by loop geometry)
Presence time: Fixed Presence time:
1.5 seconds in passage mode or
8 minutes (Limited by %∆L/L)
Response Times: Turn-on 52 ms ±3.5ms
Turn-off 52 ms ± 3.5ms
Recovery ± 75ms
Operating modes: Two position Mode selector on face-plate
1. Passage mode
2. Presence mode
Indications: The following face-plate indications are provided per channel:
1 red – detect
1 red – fault
PCB switch selection:
1. Anti – locking enable
2. Auto – retune enable
3. Configurable Presence times
4. Delay / extend options
Delay / Extend Timing:
1. Delay – 0 to 31 seconds in 1 second steps
2. Extend – 0 to 7.75 seconds in 0.25 sec. steps.
3. “Green” gating timer enabling via remote inputs.
Protection: Loop isolation transformers, zener diode clamping
on loop inputs and gas discharge tube protection
Power requirements: 12 – 40V DC
100 m.a. max input current
Relay Outputs: 1 A @ 230 V AC Single change over contact per channel
Opto Outputs: Optional model with optoisolated solid state outputs
Operating temperature range : -40ºC to +80ºC
Humidity: up to 95% without condensation
Mechanical detail:
NEMA Card Dimensions:
175mm x 114mm
Faceplate: 25mm (wide) – 1 inch
Connector: 2 x 22 terminal, 0,156 – inch contact spacing.
Cinch Jones card edge connector, 50-44A – 30M or equivalent.)