| 摘要 |
The private branch exchange controls the forming of loop to the local or the long distance exchange subscribers without additional equipments. When a local exchange subscriber requests a message sending to the whole, the communication loops are formed as: (A) a local subscriber exchange (4-2), - a function controller (5) -a local line -a local exchange subscriber for the local subscriber and (B), a local subscriber exchange (4-1) -a function controller-a long distance subscriber exchange long distance linea subscriber for long distance subscribers. The long distance exchange subscriber exchange sends thd DTMF signal tone to the long distance exchange subscribers and then the mode of the subscribers is changed into a broadcasting mode and a multifrequency dialer (MFD) signal tone is sent to the exchange. The mode change for the local subscribers is executed by reversing the polurity of DC power in the communication loop forming unit (10).
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