A basic Staco variable transformer consists of a copper winding on a toroidal core of laminated, grain-oriented, silicon steel. A carbon brush, connected to an output terminal, is rotated over the length of a precision-ground, precious metal-plated, commutator track to tap off voltage at any turn from zero volts to the maximum output voltage of the winding. Unlike a standard fixed ratio transformer, a Staco variable transformer is designed to provide variable output voltage that can be adjusted from 0 to 117% of the unit's input voltage.

Ventilated steel case with line cord, receptacle, illuminated on/off switch and fuse. 3PN prefix : three conductor line cord and matching receptacle

Manufacturer part# : 3PN1010B

Input voltage : 120Vac 50/60Hz
Variable output : 0 - 140Vac , 10 Amps maximum