Format of FaxBIOS SCHED_CLOSE command buffer:
Offset	Size	Description	)
 00h 12 BYTEs	common data (see #02935)
 0Ch	WORD	scheduler handle
 0Eh	WORD	envelope ID generated
 10h  6 BYTEs	future expansion
 16h	WORD	structure size
SeeAlso: #02945