ARRANGEMENT FOR AVOIDING UNDSIRABLE OSCILLATIONS IN A CLOSED-LOOP SYSTEM AND LOUD-SPEAKING TELEPHONE SET EMPLOYING THIS ARRANGEMENT

摘要

This arrangement has for its object to avoid sustained annoying oscillations in a looped system, such as a looped electro-acoustic system or a control system. It comprises a variable-gain amplifier (11) incorporated in a first path (C1) which forms part of the loop. Connected between the input terminal (A) and the output terminal (B) of the said first path is a second path (C2) having at least one part which is separated from the first path. Amplifier (14) is provided to ensure that the gain in the second path remains higher than the gain in the first path in the overall frequency band where the oscillations are liable to be produced. A signal (W) formed in the said part of the second path which is separate from the first path is applied to the input of a linear regulator 13, which controls the variable-gain amplifier (11) of the first path and variable-gain amplifier (12) of the second path so as to keep the signal at the input of the regulator (13) constant from a certain value of the signal (W) formed in the second path.