In addition to allowing the application to directly control RTS and DTR, the physical device driver has different automatic control modes to control the value of the output modem control signals:

• Open and Close processing of DTR and RTS
  
• Disable/Enable DTR and RTS
  
• RTS toggling on transmit
  
• Input handshaking using DTR and RTS

These control modes are described in the section on States of the ASYNC Device Driver, and in the IOCtls description.

Note: The level of support provided by this device driver requires that DTR and RTS are turned on at least once, even if this puts the physical device driver in a mode where they will never be turned on again.