I guess I accidentally activated the voice dictation and now my iPad is locked without internet connection. Now I am not able to keyin my PIN and not able to de-activate the voice dictation. Can somebody help me with this?
Do you mean the VoiceOver accessibility function or Siri ? If VoiceOver, then how did you turn it on ? If via Settings > General > Accessibility then you should be able to turn it off directly on the iPad (you need to use a tap-to-select and then double-tap to activate/type process and 3 fingered scrolling) to go into Settings > General > Accessibility > VoiceOver 'off', or you can do it by connecting to your computer's iTunes : http://support.apple.com/kb/HT4064
If you don't know how it cam on then try triple-clicking the home button and see if that turns it off, and if it does you can then change what a triple-click does via Settings > General > Accessibility > Triple-Click Home.