-.B cdtrcts
-Use a non-standard hardware flow control (i.e. DTR/CTS) to control
-the flow of data on the serial port. If neither the \fIcrtscts\fR,
-the \fInocrtscts\fR, the \fIcdtrcts\fR nor the \fInocdtrcts\fR
-option is given, the hardware flow control setting for the serial
-port is left unchanged.
-Some serial ports (such as Macintosh serial ports) lack a true
-RTS output. Such serial ports use this mode to implement true
-bi-directional flow control. The sacrifice is that this flow
-control mode does not permit using DTR as a modem control line.
-.TP