US Patent 7207912 Bicycle shift control apparatus that prevents undesirable chain angles

A shift control apparatus is provided for a bicycle having a plurality of front sprockets and a plurality of rear sprockets, wherein a front derailleur shifts a chain among the plurality of front sprockets and a rear derailleur shifts the chain among the plurality of rear sprockets. The apparatus comprises a shift unit that provides signals for shifting the front derailleur and the rear derailleur; and a prohibiting unit operatively coupled to the shift unit and providing signals so that the chain is prohibited from engaging at least one of i) a laterally innermost front sprocket in combination with a laterally outermost rear sprocket, and ii) a laterally outermost front sprocket in combination with a laterally innermost rear sprocket.