This is the value of the modem control signals Data Terminal Ready (DTR) and Request To Send (RTS) put out by the communications hardware. Each signal is controlled independently and can be either ON or OFF. See IOCtls ASYNC_SETMODEMCTRL and ASYNC_GETMODEMOUTPUT.

Initial Value

When the physical device driver starts the port during device driver initialization, their values are turned OFF.
First Level Open
The signals are normally turned ON, but there are many conditions that can cause the signals to be affected differently. See IOCtls ASYNC_SETMODEMCTRL and ASYNC_SETDCBINFO for a complete explanation.
Close Considerations
A Close request packet causes DTR and RTS to be turned OFF after the transmit hardware has completely transmitted all the data sent by the physical device driver. After processing this Close request, the port is no longer open from another OPEN without a CLOSE. In addition, at least 10 additional character times must have elapsed (or one second, whichever is less).
Mode Utility
Not applicable for direct control. Indirect effects through altering processing modes of the physical device driver are possible.

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