Int 1A/AH=80h

AH = 80h
AL = 00h source is 8253 channel 2
01h source is cassette input
02h source is I/O channel "Audio IN"
03h source is sound generator chip

Note: Although documented in the 1000TL Technical Reference, the 1000TL BIOS has just an IRET for this call

See Also: AH=7Fh - AH=83h