| 摘要 |
PURPOSE:To offer a miniature compensating circuit having excellent call characteristics, by connecting additionally a buffer amplifier and a coil to either one of windings of coupling transformers provided between a terminal device and a switchboard. CONSTITUTION:An evil effect is given to the call characteristics if an AC curent 11 flows to an AC earth point E via an energizing inductance M component of a transformer T from a channel SPI. Therefore the AC voltage V of the channel SP1 of the extension side is amplified by an amplifier K, and an AC current 12 having same phase and level as the current 11 is flowed to the 3rd winding L3 via a coil L. Thus it is possible to set the current I1 equivalently to 0. Therefore the current I1 can be set to 0 by selecting an amplifier K having a gain which satisfies K=(M+L)/M and a coil L having an inductance component. This eliminates the inductance component between a channel and an earth point and can ignore equivalently the impedance of the transformer T that is viewed at the side of an extension or an exchange. Thus no effect of inductance M is exerted on the call characteristics. |
