cant find puls wire of 87 300td needet for gps

First sorry for my bad inglish. I like to instal a blaupunkt gps in my 300 td from 1987 bud i can't find the puls wire that give's a puls as soon as the car is moving. It is someweare behind the cockpit told a friend me bud i cant find it. Please help me?

[dpetryk]

I intrepret you message to mean that you are looking for the speed pulse which comes from the driveshaft. It is one of the 5 wires connected to the black plug for the radio. The 5 wires are as follows.

(May not be in order)

1. Ground.
2. Speed pulse.
3. Battery.
4. Ignition or accessory.
5. Illumination.