| 摘要 |
PROBLEM TO BE SOLVED: To perform the no-ringing communication without using a no-ringing trunk after forming a common FSK part in a terminal network controller and simplifying the internal constitution of the FSK part by performing the communication of data with the center side in the same signal form as that which is used for the signal of the caller number signal notification service that is transmitted from a station exchange of a general telephone circuit. SOLUTION: In a standby state where a terminal device waits for the calling of the center side, a switch changeover part 15 connects a telephone set 11 to an off-hook detection part to detect the using state of the set 11 and always keeps the set 11 separated from the telephone circuits L1 and L2. When a center is started at the center side, a call signal is sent to a controller 10 from an exchange. Thus, the polarity of both circuits L1 and L2 are inverted when the calling is detected. A polarity inversion detection part 12 detects the polarity inversion of the circuits L1 and L2 and transmits the output showing the inversion of polarity to an FSK part 13 as a signal that instructs the start of an operation. |
