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. (2 wiring options available-see below)
Manufacturer part# : 221B

Input voltage : 120Vac 50/60Hz
Variable output : 0 - 120Vac , 2.5 Amps maximum
Can also be wired for variable output 0 - 132Vac (instruction sheet included)