Analog Display Services Interface (ADSI)

A complex set of standards for the telecom industry. Built off of FSK keying used by CallerID, ADSI is capable of remotely controlling a screenphone with softkeys.

Effectively, session based applications can be used when the phone is online, or scripts can be preprogrammed into the phone for when no ADSI connection has been established (on or off hook).

Originally, this technology was made by Telcos who thought they would use it to offer services to residential customers. They envisioned such features and buying airplane tickets from your screenphone. Adoption has been mixed.