Precor C846 - Precor Upright Exercise Bike features belt drive system with a double step-up drive which gives users a smooth, quiet exercise experience. The Poly-V belt is used instead of chain which also reduces the bike maintenance. A durable, built in magnetic, no-contact generator system provides consistent resistance and reduces the roughness, maintenance, and wear associated with mechanical alternators. 20 Resistance Settings, Self contained power system,Turns on when you pedal