Abstract: Simultaneous interpretation apparatus using matrix circuits whereby, even when an additional original language is used other than the specified original languages for the apparatus, simultaneous interpretation of that additional original language into the specified original languages is accomplished with ease and without hindrance. The present invention is particularly adapted to the interpretation of four specified original languages, for example Japanese, English, French and Spanish, and is particularly useful when an additional original language is used, such as Chinese for example. The matrix circuitry of the present invention enables translation of the additional original language to proceed even though the apparatus is primarily adapted for use in interpreting and translating the four specified original languages. Without this matrix circuitry the apparatus could not adapt to the additional original language since certain translators would not be alerted to perform their translating duties.