Reversing light switches
There are two main types of reversing light switch.
On a manual gearbox the switch usually screws into the gearbox casing and may have a locknut to hold it in position. This type of switch has two terminals.
On an automatic gearbox the switch is similar in appearance but usually has four terminals instead of two. Two are for the reverse light circuit and two for the inhibitor switch circuit which prevents the car being started in any gear position other than 'N' or 'P'.