TR6 Triumph TR6 PDWA Brake Question

[Got_All_4]

Cleaning up my PWDA for my 69 TR6. I removed the switch and took my volt meter and checked across the two terminals. I was surprised to get current across it. Am I suppose to? I thought that the piston pushed the post up on the bottom of the switch and made contact and turned on the light on on the dash. There is a jumper down inside the terminal which surprised me. I watched a couple of videos on You Tube and neither answered my question. So what am i missing here?
Thanks!

 

[poolboy]

Both terminals are the same and go to the same place inside the switch..they are not polorized + and - Look close.
The body of the PDWA when mounted on the car is grounded and so is the shuttle. The body of the switch is plastic--non conductive
If the shuttle shifts due to an imbalance of hydraulic pressure, the shittle presses against the plunger in the switch raising a contact patch on the other end of the plunger inside the switch which grounds both of those terminals to the Grounded PDWA completing the ground circuit for the BRAKE warning lamp
Very similar (but opposite) to the brake light switch on your TR6 brake pedal which completes the circuit when it's plunger extends