Multi Line Telephone

High level leader's office is often necessary to be equipped with telephone sets connected to multiple channels, e.g, the one of internal network, the one of city PSTN, the one of outside city PSTN and the one of the military telephone network. If these Channels can share a telephone set which is equipped with channel display and channel selecting key, it can not only save source, but also be very convenient for the user. It is not a well-solved issue up to now to develop such a telephone set which is really flexible and convenient, since it involves several key techniques and there many function details must be carefully designed.Basing on thoroughly investigation about the progress in this aspect, the research work of this thesis has some innovations as follows.1,In the aspect of hardware design, the author has solved the problem of that different channels are separated in earthing, so as to be able to avoid the interference between the earth-shared terminals.2,In the aspect of software design, the thesis has solved the problem to guarantee no miss-decoding when multiple channels are active simultaneously, as well as how to deal with the problem that another new call comes while one channel is working.3,By using a cheap single-chip computer with only two series interfaces, the call information detection in real-time for 4 channels is realized by means of the capture/ comparison function provided by Timer-B. It makes the developed product has low cost while its fiction can satisfy application requirement.The thesis has given the global scheme, system configuration, technical parameters and specifications of the related modules, the ideal of hardware/software design, as well as testing methods of the prototype. The development of the telephone set prototype is almost finished, and it would be a good commercial product with practical value.