| 摘要 |
A cellular telephony system is described, having possibly overlapping 3G and 2G service areas together with 3G and 2G handsets having inter-operability at least as far as voice calls are concerned. At least some of the 3G handsets have voice telephony (VT) capability, so that each of these handsets is able to communicate with another similarly equipped 3G handset when in a 3G service area - though not able to communicate with a similarly equipped 3G handset when it is off or unreachable in a 3G service area or when in a 2G service area - and not able at all to make VT communication with a 2G handset. The system provides a VT mailbox for receiving, storing and forwarding a VT call when addressed to a 3G handset with VT capability but not currently able to receive the VT call (because it is switched off or unreachable in a 3G service area or is in a 2G service area). If the VT call is directed to a handset not having VT capability, the system automatically invites the caller to leave a message for forwarding to the called handset, which may be a voice message or may be a video message based on the VT call and sent as an MMS message or possibly as an emailed link.
|
