3 CMD switches, 747
The L and C autopilot selections reference the Capts flight instruments for speed / altitude data and the R autopilot references the FO instruments. The APP mode arms all 3 autopilots when selected and following a successful integrity check below 1500' Rad Alt, they become active and introduce rudder input. This website reproduces some of the Boeing FCOM info and might help you:
http://meriweather.com/flightdeck/