Why not just search for the datasheet?
The coil voltage appears to be 196 to 253 V (Nominally 230V) (Actually I was quite surprised, since a lot of the SOV devices I work with are 24Vdc, but there you go)
Modulation is achieved by PWM of the solenoid supply and not varying the supply voltage. There is a detailed description on the datasheet.
At risk of upsetting certain individuals, can I point out that Google is really useful.