TD424N Four Channel NEMA format Detector

The NEMA card detector (TD424N) is compliant with VicRoads and the R&TA (NSW) specifications for use in Australia with SCATS Traffic systems. They meet the requirements of the Australian Standards and American NEMA TS1.


  • 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

878FT0020 - TD424N (Relay) - 12-24V DC

878FT0022 - TD424N (Opto) - 12-24V DC

Self tuning range: 20-1000μH
Sensitivity: Eight step adjustable on face-plate:
Step 7: 0.02% ΔL/L
Step 5 -6 : 0.05 / 0.1% ΔL/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 %ΔL/L)
Response Times: Turn-on 52 ms ±3.5ms Turn-off 52ms ± 3.5ms
Recovery Time: ± 75ms
Operating modes: Two position Mode selector on face plate
1. Passage mode
2. Presence mode
3. Channel “off”
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 (when fitted)
3. Configurable Presence times
4. Delay / extend options
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
Fault Outputs: Common open collector operates under conditions of a
loop short /open circuit
Relay Outputs: 1 A @ 230 V AC Single change over contact per channel.
Opto Outputs: Optional model with opto-isolated solid state outputs