| 摘要 |
A cellular system detects, at system level, whether a calling or a called party is a TTY type user, and in response to a positive identification allocates resources to service the TTY mode call. Several techniques are provided for detecting occurrence of TTY mode. According to one, either the calling or called user originates a function code identifying to the cellular system that the call, or part of the call, is in TTY mode. According to another, identifications of subscribers as TTY type user's are entered by service operators, at the time of initiation or change of service, into an HLR and/or a VLR of an MSC, to enable the cellular system to identify TTY type users. It also is contemplated that the cellular system detect specific cues indicative of a user being a TTY type user, and from such cues built and update TTY type user databases that will enable the cellular system to subsequently identify occurrence of a call by a TTY type user. |
