The additionnal Module R 725A enables to operate the following automatic voltage regulators (the 1ST FUNC-TIONbeing VOLTAGE REGULATION) into a so said "3 FUNCTIONS" regulation system: The2nd FUNCTIONbeing the POWER FACTOR ("COS ϕ") REGULATION, using an additionnal C.T., when the alternator is paralleling with the mains., . The 3rd FUNCTIONbeing the BALANCE (EQUALI-ZATION) OF VOLTAGESbefore paralleling (U = U) which is generally realised by a synchronizer controlling the remote voltage trimmer of the automatic voltage re-gulator