| 摘要 |
PURPOSE:To prevent malfunction of a tone detection circuit by providing a logic circuit which outputs a predetermined instruction signal decided in response to a tone number in a tone synthesis wave to a prescribed output port and stops an output when an error signal is inputted to the tone decoder. CONSTITUTION:A tone number identification circuit 4 outputs an output corresponding to a tone number by one to one through the overlap of an output of a tone detection circuit 3. That is, when no malfunction exists in the tone detection circuit 3, the output of the tone detection circuit 3 and the output of the tone identification circuit 4 are coincident and it is discriminated by a discrimination circuit 5 and in the case of dissidence, an error signal is inputted to a logic circuit 6a and the output is stopped. Thus, it is not duplicate the tone detection circuit for the redundancy processing. Thus, malfunction of the tone detection circuit 3 is prevented by the addition of a simple circuit. |
