Abstract: A digital voice switch for detecting speech signals in the presence of noise on a communication channel. The voice switch employs a threshold adjustment circuitry and three threshold detectors which include a speech detector, a noise detector and a disabling detector. The speech detector having a variable speech threshold level detects the presence of speech signals in the communication channel. The noise detector having a variable noise threshold level detects the presence of noise. The threshold adjustment circuitry, which is capable of providing rapid threshold adjustment, operates in conjunction with the noise detector to detect the noise level and to adjust the speech and noise threshold levels according to the level of the noise present in the communication channel. The disabling detector having a fixed maximum threshold level operates to disable the function of the threshold adjustment circuit while speech is present.