Abstract: An amplifier in which the gain (A.sub.i) is automatically controlled to a maximal value comprises means (D.sub.i) for detecting ringing tones and means (V.sub.i) for reducing the gain upon the detection of ringing tones. Also proposed is a circuit (D.sub.i) for detecting ringing tones. A dynamic equilibrium can be obtained by alternately reducing the gain in the event of ringing tones and raising the gain in the absence of ringing tones.

Abstract: An automatically controlled amplifier arrangement comprises a controlled amplifier unit (35), a detection unit (2) for detecting oscillations of the arrangement in the case of acoustic feedback during operation, and a control unit (3) which, in response to the detection unit (2), controls the gain of the amplifier unit (35). The controlled amplifier unit comprises separate control means for separately controlling the gain for different frequency bands (1', 1", 1'") below the howling limit. Prior to this a pre-adjustment is effected. Further, a circuit is proposed which increases the gain during preadjustment until oscillation occurs and which subsequently reduces the gain (if desired for each frequency band) until an adjustable margin below the howling limit is obtained (if desired for each frequency band).