The ignition input is pulled to ground through the 10k resistance, where the other inputs
can either be normally High (i.e. pulled to +12v through a 10kΩ resistor) or Low (i.e.
pulled to ground through a 10kΩ resistor). Input 1 is always biased low, while inputs 2-4
are biased high. The diagrams below show how to connect the inputs in both a high and
low-biased configuration:
