A control apparatus for an electrically operated bicycle transmission comprises a power supply sensor and a control unit operatively coupled to the power supply sensor. The power supply sensor senses a power characteristic of a power supply, and the control unit provides a signal to operate the bicycle transmission when the power characteristic falls below a predetermined value. Alternatively, the control apparatus comprises a running condition time sensor and a control unit operatively coupled to the running condition time sensor. The running condition time sensor senses a time interval of a running condition of a bicycle, and the control unit provides a signal to operate the bicycle transmission to a predetermined gear ratio when the time interval of the running condition passes a selected value.