ELECTRONIC AUTOMATIC SPEED CHANGE CONTROLLER

PURPOSE:To realize shift prevention at abnormality of a sensor with addition of a small scale circuit, by generating output from a controller to a speed change gear driving solenoid valve while sampling the output with an output signal from a prescribed sensor and outputting said output. CONSTITUTION:When a signal 40a from a car speed sensor 10 is lost, an output signal 40C of a differentiation circuit 42 is synchronously lost, accordingly an s input signal 40d and R input signal 40e to a flip flop 43 are also lost, and a Q output signal 40f of the flip flop 43 is not changed as left in a high level, then a solenoid 30 is not changed in a state as removed with excitation. In this way, when an output signal is lost by an abnormal condition of the car speed sensor 10, a vehicle at its high speed running can be prevented from being suddenly shifted down from the second speed shift to the first speed shift, and safety of the vehicle can be held.