A bicycle control system is provided with a switch device and a cycle computer. The fusible resistor has a very low resistance of 20 to 470 m\u03a9 by depositing thin films as a fusible element made of a material with low resistivity such as copper having a temperature coefficient of over 2,000 ppm\xb0 C. Either the number of bits per cell is held fixed or the monitored condition is an intrinsic condition of the cell. In one embodiment, a gear has teeth disposed on one surface, two opposing substantially straight sides, and two opposing substantially curved sides, with a triangular protrusion mounted on each of the gear’s two straight portions.