Historical reference: Do not rely on this information. It is very old. About this collection
Commutator, in Electrical Engineering, an important adjunct in direct-current dynamos, to cause all the electric currents which are generated in the revolving armature to travel in one direction in the external circuit. Without the use of the commutator alternating currents are produced, i.e. an oscillatory condition of the electricity is set up in the circuit without any ultimate passage of the electricity across any section of the conductor.