From: Richard <legalize at xmission.com> Ug...you're looking for Airline Control Protocol (ALC) aka SITA P1024B. The terminals speak a multidrop bisync serial protocol with 6-bit characters and next to no error detection or correction. To do anything useful, you'll need a terminal controller (PAD) and something that pretends to be IBM TPF (airline industry specific mainframe OS) running an IPARS reservation system. X.25 was usually used to connect the terminal PADs to the hosts. The good news is that all of this is very well documented and there's a whole ecosystem of companies that still support this mess. Even Cisco supports ALC in their IBM feature set for IOS, so theoretically you could use that as a PAD (I've never tried). 20+ years ago I was involved with a project to build an ALC TPAD emulator on top of SVR4 that would let us replace those clunky terminals with PCs and translate IP messages to ALC for the back end, among other things.