Specifications:GPS Speed Sender (Mini Size, Universal Type) Application: AlI kinds of Speedometer, Tachograph High Accuracy only 0. 2% deviation (mechanical speed sensor will be 3~5% deviation) Anti-GPS Stationary Drift technology. Support both Negative & Positive Pulse output with Max 50,000pules/km Compatible with different gauges with programmable speed ratio and lowest 0.5km/h speed to start. Output two speed signals which are reverse Shockproof and Circuit Protection design Pulse/Odometer Compensation when in Tunnel or under Bridge Default Speed Ratio: 5000ppk (5000 pulses per km) High quality GPS Active Antenna which performs well in windy or heavy rainy weather. Mini Size: 4. 5cm(L)x1.9cm(W), 100cm extended cable DC12V/24V Power Supply (6- 36V DC)Cable Definition:- RED: Power +, DC8~32V - BLACK: GROUND - GREEN: Speed Pulse Signal Output + - BIUE: Speed Pulse Signal Output- Please connect GREEN or BLUE cable (one of the two) to your current Speedometer/odometer/tachograph.How does it work?GPS Odometer Speed Sender provides a reliable calibration-free replacement for mechanical speed senders. Using data received from the Global Positioning Satellite network, the GPS Speed Sender calculates three-dimensional ground speed and provides a pulsed output compatible with existing mechanical speed senders. This high-technology solution eradicates the dependency on vehicle specific parameters thereby reducing installation time and eradicating the need for periodic calibration.