35w Osram Powertronic electronic ballast output.

Quick look at a 35w electronic metal-halide ballast.
Channel 1 is measuring the lamp voltage and channel 2 is measuring the lamp current.
You can see the lamp is being driven on a square-wave AC voltage of 166hz. You can also see quite a bit of overshoot on each re-ignition of the arc.

Ballast was an Osram PTi 35/220-240 S. Lamp was a Philips Master CDM-T in colour 942.