| 摘要 |
<p>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 brach 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 current is supplied CH10 to the main device at the neutral point of the office call line during the office call, and at the same time the DC is extracted CH21 and CH22 via the switch of the main wire selection button. Transistor TR20 functioning as a switching means is actuated with the above extracted current. Then privacy call relay PV is actuated when the switching means is working and hook switch HS2 of the slave unit is made each. Thus talking circuit 21 of the slave unit is cut off from the office call line.</p> |
