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;
• and
• a brake actuating mechanism connected to the braking spring, the brake actuating mechanism including a switching actuator movable between an initial state and an actuating state, and a position selector having a first hold position for holding the braking spring in the engaged state and a second hold position for holding the braking spring in the release state;
• wherein the brake actuating mechanism is configured to cause the position selector to switch from the first hold position to the second hold position through a back-and-forth movement of the switching actuator between the initial state and the actuating state, and to cause the position selector to switch from the second hold position to the first hold position through another back-and-forth movement of the switching actuator between the initial state and the actuating state.