Martindale vipd voltage indicator and proving device martindale marvipd138 p this voltage indicator and proving device from martindale offers an instant clear indication to show if a circuit is live along with its voltage range and whether ac or dc tough moulded construction and leds combined with heavy duty double insulated cable large finger guard and a retractable lockable prod sheath make this the safest most durable and reliable instrument of its type p p the pd440 proving