| 摘要 |
PURPOSE: A method, transmitting information of sending subscriber, enables TDX switching unit to send information of transmitting subscribers by a method of frequency shift keying, which has best efficiency among modulation methods changing digital data of sending subscribers to analog on the general network. CONSTITUTION: If TDX exchange unit is requested transmission, it enables a terminal of transmitting subscriber to send its information to receiving subscriber. The new TDX exchange unit sets a channel for transmitting frequency shift keying signal, when a subscriber requests to transmit it. If the receiving subscriber's line isn't engaged, the unit changes information of the sending subscriber into the frequency shift keying signal, and transmits the signal to the receiving subscriber via the channel. If the receiving subscriber's line is engaged, the unit transmits frequency shift keyed information of sending subscriber after getting DTMF(Dual Tone Multi-Frequency) start code from a terminal of the receiving subscriber.
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