At 11/10/2009 15:29, you wrote: >That is because it is patented by Motorola. > >Please refer to US Patent #3,584,304 > >US Patent #3,628,058 also describes the squelch circuit used in the >Micor and even gives a schematic for the M6709.
The latter really gives you a new appreciation for the engineering that went into that chip. Things you probably never thought of like temperature compensation were accounted for in the design. Of course, you have to get through the patentlegalize: "means coupling said output of said filter means with said input means of said first switch means;". Sheesh! Bob NO6B
