LOUDSPEAKER TELEPHONE SET

PURPOSE:To expand the operation range of an automatic loss control type voice switch circuit and to minimize insertion loss, by preventing the hysteresis width of the voice switching circuit from being negative in accordance with the degree of volume control of a receiving circuit. CONSTITUTION:In receiving status, a transmitted voice is once inputted to a control circuit 10, then returned to a receiving input by the revolution of a protective side voice circuit and inputted to the control circuit 10 again through a betaALS circuit 5. By two input signals, the control circuit 10 increases the gain of the betaALS circuit 5 up to the minimum value required for the prevension of howling. Since an output from a speaker 19 is generated in a microphone terminal input 1 also in the receiving status, the control circuit 10 can use the gain of an alphaALS circuit 3 for the prevension of howling and, therefore, increases the gain up to the necessary minimum value. In this case, the control circuit 10 limits the maximum value of the alphaALS circuit 3 so that the generation of negative hysteresis can be prevented at the time of large volume.