Attenuation equaliser for telephone exchanges - alters semiconductor crosspoint attenuation to keep value of total attenuation constant

摘要

The attenuation equaliser is used for telephone exchanges with semiconductor crosspoints. It change over the s-c crosspoint attenuation from low to high for low line attenuation and from high to low for high line attenuation. The total attenuation is thereby kept within limits simply by altering the s-c crosspoint attenuation, with the result that special circuits are not required. Where transistors are used as crosspoints, their direct current is altered so as to vary their attenuation. Where MOSFETs are used, their gate voltage is varied to set the attenuation high or low. The attenuation is set according to 'internal connection' 'external connection' or 'external private exchange'.