A shorting jack, and described above, is not the same as a switching jack. For a great guide to jack schematics, go to: http://www.switchcraft.com/
Click on 'jacks and plugs'
Click on 'jack schematics'.. download page 1 of 2.
A shorting jack looks like figure II
, where the internal path is grounded until a plug is inserted.
A switching jack looks like figure VI
, where the internal signal path is interupted by the plug insertion.