The basic closed-loop stand for testing of gears contains an energy source, SE and two identical mechanical transmissions, TM - 1 and TM - 2. The closed loop results by adding mechanical elements (such as pairs of bevel gears with the transmission ratio equal to 1). The loop is closed geometrically, mechanically and energetically. The energy is re-circled along the loop, so that the external source covers only the mechanical losses caused by friction in bearings, gears' contact etc.