INT 15 - SYSTEM - READ SYSTEM STATUS (CONVERTIBLE)
AH = 43h
Return: AL = status bits
bit 0: LCD detached
bit 1: reserved
bit 2: RS232/parallel adapter powered on
bit 3: internal modem powered on
bit 4: power activated by alarm
bit 5: standby power lost
bit 6: external power in use
bit 7: power low


1543 - SYSTEM - READ SYSTEM STATUS (CONVERTIBLE)