Check for dial tone on the line
Func AX 14h
Param DX 0 for a long test (500ms)
1 for a short test (32ms)
Return AX 1 for dialtone detected.
0 for no dial tone detected.
Delay 32ms or 500ms 
        Check for dialtone on the line.  Uses zero cross counting
        and the frequency set by DTONE_FREQ to detect dialtone.


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