| 摘要 |
According to the present invention, a voice storage device includes a port control unit for monitoring a service state of a port of a PBX extension circuit, and a private branch exchange is configured to transmit, upon receipt of an incoming call, an incoming signal including caller information and the number of a port receiving the incoming call to the voice storage device without bringing an outside line to an off-hook state. As the voice storage device receives the incoming signal, the port control unit detects the port, which is available. When the port is available, paging directed to an individual extension telephone is performed through the private branch exchange by use of this available port, and until the outside line goes off-hook, a caller keeps hearing a ringback tone with the ringing signal being sent from a telephone office to the caller.
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