the XXX input "in / on" a system

[sunsunmoon]

Connect the RCA-style audio jacks on your iPhone AV cable to the appropriate input in your sound system. Both types of AV cables will have red and white audio outputs that can be plugged into your television's audio input or your home theater receiver.
(From http://www.ehow.com/how_7633389_connect-iphone-tv-av-cable.html)

Attach the appropriate end of the connecting cable to your iPod, then connect the other to the auxiliary input on your Saab's stereo system.
(From http://www.ehow.com/how_7256262_connect-saab-factory-car-radio.html)

- the XXX input in a system
- the XXX input on a system
Do you think that these are interchangeable?

[Tdol]

With an area like IT that is developing and changing so fast and so internationally, you will find many cases of different prepositions being used. They both sound OK to me.