Stereophonic bilingual signal processor

Apparatus for identifying the form of first and second audio input signals which may be either of a matrixed stereophonic form wherein each signal comprises first and second common components or of an unmatrixed form wherein each signal comprises a respective independent component, said apparatus comprising:

• first means for combining said first and second signals to produce a third audio signal;
• second means for combining said first and third audio signals to produce a fourth audio signal;
• third means for combining said second and third audio signals to produce a fifth audio signal;
• fourth means for combining said fourth and fifth audio signals to produce a resultant audio signal exhibiting a null condition when said first and second audio input signals are of said matrixed form and a non-null condition when said first and second audio input signals are of said unmatrixed form;
• and
• fifth means for detecting said null and non-null conditions of said resultant audio signal and providing an indicator signal having a first condition indicative of said matrixed form of said input signals and a second condition indicative of said unmatrixed form of said input signals.