## Input/Output Device Driver Reference

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### Output Modem Control Signals

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.