| 摘要 |
PURPOSE:To reduce the number of control lines requiring three of them in a conventional device to two, by connecting a spark erasure circuit in parallel with a line between a central office line and a DC loop forming part, and interlocking a switch which opens/closes the spark erasure circuit with the switch which short circuits between the central office lines. CONSTITUTION:When a central office outgoing request is issued from an extension, a dial shunt relay 17 is closed, and afterwards, a dial relay 15 is closed, and the central office line is captured. A section where the dial shunt relay is closed is a break time, and the contact of the dial relay 15 is connected to an incoming detection circuit part 4, and a DC component is removed by a capacitor 18 for cutting the DC component and the capacitor 7 of a spark erasure circuit part 6, thereby, a DC loop is set at an open state. By repeating such operation, a DC pulse signal is sent to the central office line. During sending a dial pulse signal, the spark erasure circuit part 6 functions at the time of making contact.
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