The PD690 proving unit produces 690V AC/DC to enable voltage indicators to be fully checked.
This unit is suitable for indicators with 230V and 415 / 440V AC or DC detection ranges,
such as the Martindale VI13700G.
The PD690 is one of the few proving units to check indicators with ranges above 250V.
The PD690 can also check Drummond and other filament lamps due
to its output being sufficient to illuminate the bulb.