SBD have now available a new Kill Switch, it has been specifically developed for the MBE9A9 and MBE9A6 ECUs. It gives a huge increase in protection for all the electronic systems and components on your car and the ECU controls the kill switch.
Effectively when either the internal or external kill switch button is pressed, the ECU turns off all external outputs shutting down components such as fuel pump, coils, injectors, etc. then disconnecting the kill switch itself milliseconds later. This has several safety advantages, because effectively the engine has been stopped any current that was coming from the alternator or being used by systems on the car are turned off so when the kill switch disconnected there is no chance of a large spark. It also protects all the electronic systems due to the fact that there is no current surge when the kill switch operates.
The car is normally installed with 2 Off buttons, one external and one internal and the driver has an additional On button to turn the kill switch on.