English: A schematic showing the ignition/steering wheel lock of a car. Note that the 4 wires are not connected from a single wire, they are seperate (the schematic was made how it is because I wished to clarify that they run next to each other, rather than under each other, when viewed from the side). Note that 4 is generally connected to the largest power consumers (ie main lights, rear window heater, windscreen wipers, cigarette lighter, ...), 5 generally connects to smaller power consumers.

Note also that most car ignition/steering wheel locks also have 4 modes:

• In mode 0: main engine is off (or is stopped if the engine was already on), 4, 5 & 7 are not connected to 6
  
• In mode 1: 4 is connected to 6
  
• In mode 2: 4 and 5 are connected to 6
  
• In mode 3: 4, 5 and 7 are connected to 6; note that this 3rd mode is springed, meaning that the key will spring back to mode 2 upon release of the key. This is because the powering of the starting engine is no longer wanted once the main (internal combustion) engine has kicked on.
  

The schematic was made based on the http://commons.wikimedia.org/wiki/File:KEY.png image and by following a schematic from the book "Zo werkt uw auto" by Rien Tholenaar and Carel Zaal