| 摘要 |
PURPOSE:To select an equalizing circuit automatically by transmitting reception level information on a test tone by utilizing the interruption of earthing. CONSTITUTION:A signal f0 (test tone) from an oscillator 1 is inputted as an upper limit equivalent to a line frequency from the voice input terminal A of a channel converter 2 and then detected by the level detector 8 of a party station through a cable 5. The detected level is converted into an interruption signal of earthing by an encoder 9. This interruption of earthing is inputted to a dial signal input terminal B and then received through a cable 13 as the interruption of an f1. The same operation is performed at proper intervals between the upper limit and lower limit of the transmission frequency band of the transmission line 5. On the basis of interruption level values of earthing received corresponding to those respective points, an arithmetic device 16 calculates the amplitude distortion of the cable and then controls a line equalizer 4 by using the calculation result. |
