| 摘要 |
PROBLEM TO BE SOLVED: To provide a telephone exchange which completely restores even an extension telephone set operated, based on a different control information system between before occurrence of an error and after changeover to cope with a flexible system that is a requirement for a recent telephone exchange. SOLUTION: This telephone exchange detects communication error caused on a communication channel through asynchronous state of communication between extension telephone sets 20, 40, 50 and the telephone exchange and when the communication error is restored within a prescribed time, type information of telephone set is requested to the extension telephone sets 20, 40, 50. When the type of the telephone set differs before and after the occurrence of the error as a result of identifying returned type information, control data are converted into data in matching with the type of the telephone set after the restoration to control the extension telephone sets 20, 40, 50 contained in a channel where the communication error takes place.
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