COM_DTR()
 Queries/sets the Data Terminal Ready (DTR) status
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 Syntax

     COM_DTR(<nComPort>,[<lNewDTRStatus>]) --> lOldDTRStatus

 Arguments

     <nComPort>  Designates the port (1 to 4) on which DSR is tested.

     <lNewDTRStatus>  Designates the status of DTR.  .T. designates that
     the DTR signal is active, and .F. designates that the signal is
     inactive.  If the parameter is not specified, CA-Clipper Tools does not
     affect the DTR exit signal.

 Returns

     The returned value corresponds to the DTR signal status prior to the new
     setting, or in the absence of <lNewDTRStatus>, the returned value
     corresponds to the current DTR.  A return of .T. indicates that the DTR
     is active (MCR bit 1 = 1).  A return of .F. indicates that the DTR is
     inactive (MCR bit 1 = 0).

 Description

     COM_DTR() queries the DTR signal status.  If the second parameter is not
     supplied, the DTR signal status does not change.

 Note

     .  The COM_CLOSE() function resets DTR (to inactive).  By
        contrast, COM_OPEN does not automatically make DTR active!

 Example

     A COM_OPEN() does not set the DTR signal.  You must specifically set the
     DTR signal.

     nBuff_size  :=  4000                      // 4000 byte buffer
     lComOk      :=  COM_OPEN(1, nBuff_size)   // Open COM1

     IF lComOk
        COM_DTR(1, .T.)                        // Activate DTR Port 1
        * ...
     ENDIF