| 摘要 |
PURPOSE:To decrease the entire communication time by sending a unique call signal from a caller side and detecting in a full duplex mode the unique call signal and a called station identification signal by a called party side. CONSTITUTION:A tonal signal (comprising a call signal CNG and a unique call signal NCNG) from generating circuit TNGEN is sent to a telephone line LINE via an adder 2, an attenuator 3, a HYB 5 and a NCU 6. A received signal from the LINE is separated to three paths a-c of a NEF9 eliminating a carrier (2,100Hz+ or -15Hz) of a caled station identification signal CED, for a MODEM 4 and for tonal detection via the NCU 6, the HYB 5 and a BPF 10. The paths b, c are switched by a switch 8 and fed to a tonal detection circuit (TNDET)7. Then the signal NCNG in the full duplex made with the signal CED is detected by the called party side.
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