[mylesdw]

It sounds like it's working fine. When the handbrake is on, there is no air pressure and the spring brake pulls the rods, which pulls the wedge which expands the shoes applying the brakes. When the handbrake is off, the air pressure compresses the spring brake, which pushes the rods which pushes the wedge which releases the brakes.

For the handbrake the spring applies the brake and the air pressure takes the brake off. It's a fail-safe thing - when there is no air pressure the brakes come on.