Multiple Function Detectors

Multiple Function Detectors

'Security and Flexibility Combined'

Microprocessor based dual channel vehicle detectors are ideal for use in traffic control and toll equipment vehicle detection applications

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Product Features & Benefits

The TD250 is designed for ease of installation with front panel switches for setting presence times and sensitivities and operating frequency plus four operating modes.

It provides outputs in the form of LEDs on the faceplate and change-over relay contacts. A common fault relay provides an output in the event of a faulty loop or a power failure.

Two main models are available, both providing the option of  2 separate vehicle presence outputs per channel plus 3 further operating modes:

The TD250D provides: Direction Logic (AB), Delay Mode, Extend Mode

The TD250L provides: Direction Logic (AB), Speed Logic, Headway Logic

An output will be provided when pre-set speed or headway threshold has been exceeded, and can be utilised for switching variable warning signs or for gathering traffic statistics.


  • Comprehensive diagnostic capabilities allow for accurate diagnosis of loop and installation problems
  • The loop isolation transformer provides protection against lightning, transient damage and allows for operation with single point to ground sensor loops
  • Visual loop fault monitor helps in localising the fault in the event of a maintenance call-out
  • Adjustable Presence time with a choice of four presence output settings
  • Direction Logic Option used to establish the direction of vehicle travel with an output provided for each direction
  • Delay Mode (TD250D) where a vehicle must be present for a pre‑set time before the detector will operate
  • Extend Mode (TD250D) where the detector output responds immediately to a vehicle’s presence and remains for the selected time after a vehicle has departed the loop
  • Speed Mode (TD250L) where an output relay provides a pulse output when a pre-set speed threshold has been exceeded
  • Headway Mode (TD250L) where each channel independently monitors and measures the interval between vehicles in seconds and provides a pulse output in the event of the vehicle headway being less than the pre-set threshold


Self-tuning range: 15 to 2000μH
Sensitivity: Four step selectable:

High 0.02% DL/L

Medium-High 0.05% DL/L

Medium-Low 0.1% DL/L

Low 0.5% DL/L
Frequency: Four step switch selectable - 20 to 150 kHz

(Frequency dependent on loop geometry)
Presence Time: Four step selectable:

1 Second, 4 Minutes, 40 Minutes, infinity
Pulse: Output Approximately 150ms
Indications: 1 x Run Indicator – Red Steady On

1 x Tri-coloured LED per channel
Detect Outputs: Sealed relays rated at 1A @ 220V AC

Single changeover contact per channel
Output Relay: Mode Switch selectable

(Presence relays are fail-safe)

1. Normal (Presence)

2. Direction Logic

3. TD250D – Delay; TD250L- Speed
Fault Output: Common fault output

Change over relay contact
Reset: Push button on front panel
Delay Timings: Delay turn-on 30 seconds in 2 second steps
Extend Timing Delay: Turn-off 7.5 seconds in 0.2 second steps
Delay Extend Override: 230V AC input overrides delay times
Speed Logic Option: 0 – 150kph in 10 kph steps
Headway Logic Option: 0 – 3 seconds in 0.2 second steps
Surge Protection: Loop isolation transformers, Zener diode clamping on loop inputs and gas discharge tube protection
Power requirements: TD252, TD250L:
230V AC +/- 15% (48 to 60Hz)

24V DC +/- 15%
150mA maximum input current
Operating Temperature: -40°C to +80°C
Humidity: Up to 95% RH without condensation
Housing material: ABS blend
Mounting Position: Shelf mounting
Connections: TD252 / TD250L 2 x 11-pin submagnal type
Accessories: All flying leads supplied