| 摘要 |
An exchange system minimizing ring noises generated when processing an incoming call. Upon receipt of an incoming call from a central office line, the exchange system generates a ring to a called extension telephone to which the incoming call is terminated. Thereafter, it is determined whether there is an extension telephone designating a phone number of the called extension telephone. If there is the extension telephone designating the phone number of the called extension telephone, the exchange turns on/off a lamp prepared in the extension telephone or generates a ring to the above extension telephone, after an elapse of a predetermined time.
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