| 摘要 |
PURPOSE:To easily execute a switching operation by setting the last transition delay signal of a line switching signal which controls a first switching unit as the control signal of a second switching unit and controlling a non-instantaneous interruption switching unit with a first transition delay signal of the line switching signal. CONSTITUTION:When the line switching signal rises, the switching unit 8 is switched to one contact side and at the same time the switching unit 9 is switched based on the last transition delay signal. And also a non-instantaneous interruption relay 10 is switched to one contact side based on the first transition delay signal after completing the switching of the switching unit 9 and a telephone set connection terminal is separated from a two-wire terminal. Next when the line switching signal breaks, the switching unit 8 is switched to another contact and at the same time the switching unit 10 is switched to another contact side based on the first transition delay signal. The switching unit 9 is switched to another contact side based on the last transition delay signal after completing the switching of the switching unit 8 to be in the connection of holding state. By switching to be connected to a four-wire circuit and two-wire circuit, the switching operation can be made easy and the constitution of a circuit can be simplified.
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