| 摘要 |
PURPOSE:To prevent howling while maintaining impedances in a balancing state by connecting an amplifier to the neutral point tap of a hybrid transformer at a master device side of an interphone. CONSTITUTION:A master machine 1 and a slave machine 2 call by microphoes T1 and T2 and speakers R1 and R2, and two-way characteristics are preserved by hydrid transformers HT1 and HT2. Here, when a signal from a master device 1 is sent, impedances Z11 and Z12 at both ends of a hydrid transformer are in balance, the signal is not outputted to the speaker R1 side at the master device side, and howling will not occur. When the signal from the slave device 2 is sent, an impedance Z21 is ''0''OMEGA, and by setting the neutral point tap to zero electrical potential and obtaining a low input impedance, the signal is not sent to the speaker R2 and howling can be prevented. |
