tw_MdDial( cNumber )
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     Send a telephone number to the modem and dial it. the modem
     remains engaged until the SPACEBAR is pressed. This version uses
     the Hayes AT commands. The dial string is preceded by 'ATDT'.

       Arguments:

     cNumber - 'C' a telephone number

       Return:

     NIL

       Example:

     tw_MdDial( 416-628-5086 )