An automatic attenuation circuit comprises a variable loss attenuation circuit that drives circuitry for detecting the level of the output signal of the variable loss attenuation circuit. The level detector drives a periodically reset integrator, which in turn feeds a signal to a comparator, also responsive...http://www.google.es/patents/US4276604?utm_source=gb-gplus-sharePatente US4276604 - Automatic attenuation circuit
