Gears 1 and 2 rotate about fixed axes A and B. Gear 2 has teeth c located on its end face. Gear 1 has one tooth a and locking ring b. When driving gear 1 rotates continuously, driven gear 2 rotates only during the periods that tooth a engages a tooth c. After tooth a runs out of engagement with tooth c, locking ring b slides along the inner surfaces of two adjacent teeth c, locking gear 2 against unintentional motion during its long dwell period. To each revolution of gear 1, gear 2 turns through an angle equal to ϕ=2π/z₂ where z₂ is the number of teeth of gear 2. An impact occurs when teeth a and c come into engagement.
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