INT 15,43 - Read System Status (convertible only)

	AH = 43h


	on return
	AL = STATUS:

		│7│6│5│4│3│2│1│0│  AL
		 │ │ │ │ │ │ │ └──── LCD detached
		 │ │ │ │ │ │ └───── reserved
		 │ │ │ │ │ └────── RS232/parallel powered on
		 │ │ │ │ └─────── internal modem powered on
		 │ │ │ └──────── power activated by alarm
		 │ │ └───────── standby power lost
		 │ └────────── external power in use
		 └─────────── battery low