I/O Ports on HP 48/49/50 Calculators

Type	Subtype
-33 CF Wire	-78 CF USB
-33 CF Wire	-78 SF RS-232 Serial
-33 SF Infrared	-127 CF IrDA
-33 SF Infrared	-127 SF HP-IR

“HP-IR” is the infrared system used by the HP-48,
and is not available in most of the subsequent models.

Models that are missing one of these four ports
use the alternative, e.g. the HP 50g has no HP-IR,
so it always uses IrDA, regardless of the setting of flag -127.
The HP 49G has no USB or infrared, so it always uses
RS-232 Serial, regardless of any of these flag settings.