Reception volume limiting circuit

Claim 1

A reception volume limiting circuit for converting reception speech data as a digital code into an analog receiver driving AC signal, comprising: a detecting section for performing detection/rectification and smoothing of the receiver driving AC signal and outputting a DC signal corresponding to a level of the receiver driving AC signal; an A/D conversion section for converting the DC signal from said detecting section into a digital signal; a control section for calculating a time average value by averaging the digital signal from said A/D conversion section every predetermined time interval, correcting the time average value by adding it to a currently stored attenuation amount, comparing the corrected time average value with a predetermined threshold value representing a critical sound pressure for protection of listener's hearing, calculating an excess level from a difference between the corrected time average value and the threshold value when the corrected time average value exceeds the threshold value, storing the excess level as a current attenuation amount, and outputting a volume attenuation command having the excess level as an attenuation amount; and a speech data calculating section, having means for attenuating a reception volume level by performing subtraction processing of the reception speech data, for performing subtraction processing of the reception speech data, in response to the volume attenuation command from said control section, on the basis of the excess level included in the command and outputting reception speech data attenuated by a value corresponding to the excess level.