tail lamp switch/relay????

[russellmarling]

I need some help identifying this mysterious electronic device. It makes the tail lamps come on when you turn the headlights on. It is rectangular and it has a dark green and a light green wire going to it. The wiring diagrams refer to it as the BKNG. LP. SW. This is not the stoplight switch that is mounted to the brake pedal assembly. What is this called and where can I get a new one? More importantly, where does it mount and what "flips the switch"? I know my description is vague, but this is all I know to say. Any help will be greatly appreciated.