c. Rotate  both FREQUENCY  adjust potentiometers  to obtain the same frequency  indication on both sets. Ensure  load contactor at load is open. d. Position and hold AC CIRCUIT  INTERRUPTER switch,  on  generator set  No.    1, to CLOSED until  indicator lights. e. Place the UNIT- PARALLEL switch on both units in PARALLEL position. CAUTION If  synchronizing lights on generator set No.    2 do not glow bright and dark in unison, the phasing is wrong. Shut down  generator sets and check that load cables are  connected properly. Failure to observe this caution  can result in damage to  generator sets. f. Observe  synchroni- zing lights on generator set No. 2. The lights should be glowing  bright  and dark in unison. ARMY  TM  9-6115-645-10 AIR  FORCE  TO  35C2-3-444-11 MARINE  CORPS  TM  09244A/09245A-10/1 g. Adjust  frequency  of generator set No. 2 until  synchronizing lights glow bright and dark in unison at 2 to 3 second internals. CAUTION Check that load contactor at load is open before  attempt- ing to place generators  on the line. Failure  to observe  this caution  can result in damage to  generator sets. h. When  both synchronizing  lights are  dark,  position and hold AC CIRCUIT INTERRUPTER  switch of generator set No. 2 to the CLOSED position  until indicator lights. NOTE The  generator sets are now operating  in parallel  with  no load. i. Rotate  FREQUENCY adjust  potentio- meter  of  generator set No.    1 until kilowattmeter (PERCENT POWER) indicates approximately  “O”. 2-27