| 摘要 |
PURPOSE:To save the labor of a caller and to improve a service by temporarily holding a line, feeding a signal to the caller and newly transmitting another extension designating signal when a designated extension telephone set is busy. CONSTITUTION:Even when the extension telephone set 3 designated by the extension designating signal received by a PB receiver 7 is busy, a private branch exchange 1 feeds an extension designating receiving completion signal to a station exchange 2 and the exchange 2 transmits a ring tone to a called telephone system. Thereafter, the exchange 1 feeds the second response signal to the exchange 2, temporarily holds the line from the exchange 1 via 2 to the called telephone set, transmits a dial tone from a signal generator 8 to the exchange 2 and the exchange 2 feeds this dial tone to the called telephone system in place of the ring tone. The caller understands that the telephone set 3 is busy by the change of the ring tone to the dial tone and dial-inputs the extension designating signal for designating the extension telephone set 4. The exchange 1 receives it, and then sets the line to feed the ring a call signal to the telephone set 4 and feeds the ring tone to the exchange 2. When the telephone system responds, the communication state is produced.
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