how does the passive starter kill relay work?

I was able to wire up this relay as shown, but can someone explain how the relay on the left stays engaged just by pressing the momentary button on the right relay?  I thought in order for the Pin 87 & Pin 30 to stay connected it would need a constant energy source?

https://www.the12volt.com/images/pasivestarterkill.gif

netZ

It's called latching, and it's pretty cool.

When the button is pushed, both relays engage as usual.  But notice that in the relay to the right, pins 85 and 87 are connected.

When the user pushes the button, the relay on the right sends power through 87... which also goes to pin 85 which is the turn-on trigger for the relay................... so 87 is feeding power to 85....... and 85 of course makes the relay stay on.....which of course sends power out through 87......which of course sends power to 85................... you get the idea.  Until something comes along to interrupt this process, the relay will stay latched on forever.

So it's actually the relay on the right that latches itself on.  And then its output is used to trigger the left relay, which is wired pretty normally.

Since the pink wire in the circuit is fed by the car's ignition, all you have to do to unlatch the relay is turn the key off.