| 摘要 |
PURPOSE:To obstruct an inductive disturbance current from a telephone circuit, to prevent a malfunction of a circuit and an S/N deterioration of a transmitting signal, and also to perform a data transmission using a general subscriber telephone circuit, by connecting a longitudinal current obstructing coil to a subscriber telephone line. CONSTITUTION:A subscriber telephone line 17 or a telephone set connecting line 18, and a cable 19 side of a meter 7 are separated by an AC coupling transformer 53 and a transformer of a power source circuit 54. Also, as for a longitudinal current obstructing coil 51 and 57 coupled to the telephone line 17 and the connecting line 19, respectively, directions of two windings L1, L2 on the same core become the same, the internal circuit becomes high impedance against between L1 and the ground, and L2 and the ground, and the inductance cancels each other and becomes zero-impedance against between the lines of L1-L2. As a result, a longitudinal current to the meter side from the telephone line 17 or the connecting line 18, and a longitudinal current to the telephone line side from the meter side are obstructed. |
