The ProTran1 DualPower ProLight  - for Extra Reliability and Redundancy the Protran1 DualPower ProLight indicates the presence of dangerous DC Voltage on a Light rail, Subway and Third rail line.  Simply connect the light as instructed below and the unit is functional alerting personnel of dangerous DC Voltage. The unit also indicates the non-presents of DC Voltage.  Adjustable from 0-49 VDC the unit will indicate no voltage presence with a Green LED Light.  Anything higher then the set max voltage of 1-49 the unit will indicate voltage is presence with a Red LED Light up to a max of 1000VDC