| 摘要 |
In lossless or low loss conferencing systems it is customary to use a hybrid to convert each station from 2-wire to 4-wire operation. Because of impedance mismatch conditions, reflections can occur at the hybrid interface thereby causing echo and "singing" problems. Self-cancellation of the reflected signals can be achieved by reversing the phase of the reflected signals through the hybrids and assigning the reversed phase hybrids only to stations connected to the system by trunks. For those stations connected to the system by lines, 5dB pads are used in conjunction with unreversed phase hybrids. In this way complex switching is avoided. |
