| 摘要 |
PURPOSE:To ensure both the office call and the extension call independently from each other with the minimum number of insulated conductors for the key telephone system of the branch connection system, by forming the connecting cord for the office n circuit with 2n+2 pieces of insulated conductors. CONSTITUTION:Main wires L1 and L2 plus office call line 41 within the key telephone system form a DC loop each and also isolated from each other in terms of DC to be furthermore connected T2 to each other in terms of AC. At the same time, the branch connection is secured between the office call line and each of slave units 20 and 30. In addition, the DC is supplied CH10 to the main device at the neutral point of the office call line. Then holding operation HK1 is carried out only when each slave unit is busy. And the DC is extracted CH21 and CH22 via holding switch means HK1, and then this extracted current is detected to detect the holding via holding detecting means 5. |
