I have a MacBook 3,1 and when I connect headphones or speakers to the headphones socket, audio comes out of the headphones and the MacBook's internal speakers.
I suppose this means that the function of switching from speakers to headphones is software or firmware controlled.
I have a MacBook 3,1 and when I connect headphones or speakers to the headphones socket, audio comes out of the headphones and the MacBook's internal speakers.
I suppose this means that the function of switching from speakers to headphones is software or firmware controlled.