Window shade and actuating system thereof

An actuating system for a window shade, comprising:

• a transmission axle rotatable about a longitudinal axis thereof;
• a braking spring having an engaged state adapted to prevent rotation of the transmission axle, and a release state allowing rotation of the transmission axle;
• a brake actuating mechanism coupled to the braking spring and including a switching actuator, the switching actuator being operable between a first and a second position to switch the braking spring between the engaged state and the release state, wherein the first position of the switching actuator corresponds to the engaged state of the braking spring, and the second position of the switching actuator corresponds to the release state of the braking spring;
• and
• a detent mechanism coupled to the brake actuating mechanism, the detent mechanism being switchable between a first biasing state where the detent mechanism applies a first biasing force that assists in keeping the switching actuator in the first position, and a second biasing state where the detent mechanism applies a second biasing force that assists in keeping the switching actuator in the second position.