RPM sensor Peugeot Boxer 2.5 TD

Hello everyone, someone can define how to get the information from the RPM from the engine from the captor located in the speed box.
It has 3 cables, identified in the tab as 1 2 and 3,
I need to connect a cruise speed control and so that it is activated, it must have a rpm signal.
It would seem that this captor only serves to measure the RPM, since when the engine has unplugged it has not had problems of marching and/or starting.
Thank you so much.

1 12 V
2 feeding Signer
3 MASS MASS

The signal signal is sinusoidal and occurs between 2 and 3 as a small voltage variation.

Between 1 and 3 there are 12v with positive contact to feed a primary coil that generates the magnetic field of the sensor.

All the best.