| 摘要 |
PURPOSE:To decrease a tester and a measuring instrument conveyed to a field by connecting a remote existing system and a system for debugging at a plant, a software center, etc., with a public telephone network and executing the test with the exchange program used actually. CONSTITUTION:From a telephone set 7 accommodated into an existing local exchange 14, the telephone number of a telephone set 11 (or the telephone set 7 from the telephone set 11) close to the place where a debugging system 12 is provided is dialed, the telephone set 7 and the telephone set 11 are connected and respective subscriber lines are changed over to a tester 4 side when the calling can be confirmed between both. Thus, the tester 4 at a new trunk 3 side of a tested device and a tester 8 at the debugging system 12 side are connected through the public telephone network of the local exchange 14, trunk exchanges 15 and 16 and a local exchange 17 and the digital signal modulated to a sound band is transmitted. This does not depend upon the type of the public telephone network to link local exchanges 14 and 17, and when the telephone line exists, the interface test can be executed with any exchange in the world.
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