You have a 50 hz, repetitive pulse train, with a variable duty cycle signal. No telling what you will get if you just hang a voltmeter off the signal (just some average voltage), but with an oscilliscope you can see it

The "on" pulse width varies from about 1 msec to 2 msec.

Servos have worked this way for about 25 years I would guess

The valves that jettronic makes have a small computer in them that can interpret the signal, and allow you to program the linearity of the of the braking system to a certain degree.

The computer has an output to control the valve, and it is a bit smaller than the valves we sell for the turbine shut off valves