[2] When over-braking, the Decelostat will detect rapid deceleration of wheel rotation caused by creep in the wheelset, another condition preceding the wheel-slide.
The function of the controller component is to detect the situations, such as a rapid deceleration in excess of the limit, in order to activate the valve unit.
For example, a system that uses flywheel to read and detect deceleration beyond the limit can directly send signal to the valve component.
[2] In the 1930s, Westinghouse Air Brake Company developed a wheel slip control system, first in an electrical type.
The generator was connected to a controller which contained a series of capacitors and relays in the way that the detection could be done when wheels turned in either direction.
When the wheels were rapidly decelerating, the voltage would be dropped at a high rate causing the capacitor to discharge reversely through the pick-up winding of the corresponding relay.
In a pneumatic system, this causes a valve to be open and makes the protection and dump values to release air break pressure.
In an electro-pneumatic system, this causes an electric circuit to trigger the control module to activate the release of the air brake pressure.
When the flywheel of the Decelostat detects a sharp deceleration of the wheel, the valve that relieves air pressure from the brake cylinder is actuated.
Momentarily, the wheel speeds are back in sync with the flywheel, causing the Decelostat to close the valves to resume braking again.
The principal of operation was still the same as in the pneumatic version by having the flywheel with a preset amount of optimal braking with deceleration rate without runway skidding.
The system used the same flywheel technology to detect rapid rate of deceleration, but used the electronic circuit to control the valves.
The system was used in rail cars in the late twenties century as an alternative to pneumatic Decelostat of Westinghouse.
[1] In aviation, Dunlop introduced an antiskid unit called Maxaret in the 1950s using the flywheel concept similar to the Decelostat.