| 摘要 |
PURPOSE:To reduce scanned point in a trunk and scanning circuits by providing a pattern control element which puts circuits in front and rear modes by switching and further by providing a circuit which selects a scanned circuit corresponding to the switching state. CONSTITUTION:When incoming arrives from a main wire, relay R operates to place contact (r<0>) at a scanned point on a rear side, so that a scanning circuit will be formed of terminal SCNR, contact (r<0>), break side of contact (s<2>), and terminal SCNR. A common unit supplies positive pulses to terminal SCNR through the scanning circuit. Since relay S which supplies control pattern information for the common unit is reset even if contact (a<0>) expressing a calling state is at any position, positive pulses are outputted through contact (r<o>) by way of a feedback loop at a S<2> break contact side and the close state of contact (r<0>) is read by the scanning circuit and sent to the common unit. Consequently, resistance diodes for each scanned point and terminals of a trunk can be reduced in number. |
