A code generator includes a plurality of storage elements (such as flip flops) connected to form a code-producing series, wherein the output of the final storage element in the series in connected to the input of the first storage element in the series to form a circuit and outputs and inputs of the storage elements are recursively connected means of EXOR gates. The first input of at least one EXOR gate is connected to the output of a storage element disposed in the code-producing series, the second input thereof is connected to the output of another storage element disposed in the code-producing series, and the output thereof is connected to the input of the storage element which succeeds the storage element connected with the first input of the EXOR gate. The output of a storage element disposed in the code-producing series is connected to the input of an inverter and the output of the inverter is connected to the input of another storage element disposed in the series.