INTRODUCTION These laboratory rheostats are wound on tubular cylinders of porcelain. Resistive Constantan alloy is anchored onto the collar-shaped ends, slider with copper-silver contacts connected with safety terminals (Ø 4 mm). Protection against indirect contacts by pierced sheet steel with protection degree IP 20. Rheostats of RP-1 line have only one resistor, whereas rheostat mod. RP3f includes three resistors. Supply with THEORETICAL – EXPERIMENTAL HANDBOOK