Sets the DDFlags of a key packet, instructing the keyboard device driver to send a special monitor packet down the monitor chain. This packet is sent on every Read request seen by the physical keyboard device driver for a particular screen group, and continues until the screen group is terminated or a subsequent call disables Read Notification.

The Process ID (PID) of the first caller of this IOCtl in the system is saved by the physical Keyboard device driver. Subsequent invocations of this IOCtl by a different PID result in an UNKNOWN_COMMAND error.