Remote controled weapons in WWII

Numerous bombers and heavy fighters, especially thowse that entered
service post 1943 have reference to remote controlled weapons.

Now, the remote control part should be fairly easy, but how were
they aimed? I'm assuming that you linked the gunners controls in such
a way thatthe gun always fired at the point where he was aiming,
making allowences for the location of the gun-- but how effective were
they? How hard was it to keep them in repair, as that sounds like a
fairly complex and advanced system for the 1940's.