The dummy cameras are housing SPYPOINT cameras sold without any electronic pieces. Viewed from the outside, they all look like a real camera, but empty inside.
Ideal to discourage thieves. When they spot the box, they usually leave the scene, but they can sometimes be inclined to steal them.
If a “Dummy” camera is placed in view while a real one is securely concealed, this latter one will secretly photograph the thief in action.