User's Manual

301UM0031_01 TD136 Enhanced Vehicle Detector User Manual Page: 13 of 29
4.2 Detector Sensitivity
Sensitivity of the detection system is dependent on factors such as loop size, number of turns in the
loop, feeder length and the presence of metal reinforcing beneath the loop.
Sensitivity levels of the TD136 Enhanced Vehicle Detector have been carefully optimized for traffic
control applications.
The nature of the application determines the required sensitivity, which may be adjusted by means of
the sensitivity, switches on the front of the enclosure.
4.3 Modes of Operation
In the presence mode the detector will give a continuous output during the presence of a vehicle over
the inductive loop providing that the preset time has not expired. Upon expiry the detector will undetect
and tune out the vehicle over the loop.
The presence output is known as a fail-safe output. This implies that in the event of a power failure the
detector will give a detect output. The fault relay is also failsafe and will generate an output whenever
a loop is faulty or the unit is unable to tune to the loop.
4.4 Response Times
The response time of the detector is the time taken from when a vehicle moves over the loop to when
the detector gives an output.
The response times of the TD136 Enhanced Vehicle Detectors have been adjusted to provide
adequate response to vehicles in traffic control applications.