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The escape wheel is essentially a cam even though most people think of it as a 15 tooth gear. Each pallet jewel must perform two different functions. The angled ends of the pallet jewels are cam followers and their job is to transmit motion from the cam face of the escape wheel to the pallet arm. The angle of the jewel faces determine the amount of force and the distance of movement for the cam action. If you position the mechanism with the escape wheel and the pallet jewels facing you, the OUTSIDE surface of the left pallet jewel acts as a pawl in a ratchet mechanism. On the right hand pallet jewel it is the INSIDE face that acts as a pawl. The depth of the pawls (the lock) is determined by the position of the banking pins. When the balance wheel spins around and knocks the pallet arm, it unlocks the pawl (pallet jewel) allowing the cam action to take place on the angled end of the jewel and push the pallet arm. This transmits force through the pallet arm to the roller which throws the balance arm around and winds up the hairspring. When the lever arm hits the banking pin it sits and waits until the hairspring spins the balance mechanism in the other direction and the process repeats.