The High Court in Glasgow heard William Kinnon, 52, of Dalry, Aryshire, stormed into the Burns Tavern pub, in Irvine, where 42-year-old Michelle Buckley was sitting.
She heard a buzzing sound and felt an electric shock on the left hand side of her neck.
Ms Buckley slapped Kinnon on the face and he punched her two or three times before a pub customer dragged him away.
Advocate depute Angela Gray, prosecuting, revealed that luckily Ms Buckley's neck did not receive the full force of the electric shock as she was wearing a scarf.
Kinnon admitted assault and Judge Lord Bannatyne deferred sentence until July 15.