Abstract: Disclosed is a circuit for determining whether an incoming signal is a speech signal or a data signal. In the preferred embodiment, means for separating the incoming signal into a low frequency component and a high frequency component are provided. The low frequency component consists of frequencies below a specified frequency, namely 1000 Hz. and the high frequency component consists of frequencies above 1000 Hz. Means are also provided for the comparison of the energy level of the high frequency components with a multiple of the energy level of the low frequency components. Also, means are provided for comparing a multiple of the energy level of the low frequency components with a maximum threshold and for comparing the energy level of the high frequency components with a minimum threshold. Further, means are provided for detecting whether the incoming signal has a slope.

Abstract: Disclosed is an automatic gain control circuit for a communications system, such as a time assignment speech interpolation system, which equalizes the loss in each of a plurality of transmission facilities by providing a symbol generator at a remote location for generating a test signal of predetermined amplitude. At a near location, the received test signal is applied to a controlled gain circuit for each facility, which is under the control of a central microprocessor provided with a reference signal for comparing the received test signal against the reference signal. The gain of the controlled gain circuit may be increased or decreased in accordance with the comparison of the received test signal with the reference signal. In one embodiment, the sum of the digital samples of the received test signal is compared against a reference value stored in a digital memory. In the preferred embodiment the stored reference value comprises a low and a high value which define an acceptable amplitude range therebetween.

Abstract: Disclosed is an echo suppressor circuit which provides a variable loss in a speaker's transmit path, which loss is a function of the relative speaker volumes. The loss provided in the path of a particular speaker is relative to the volume of the speech emanating from each speaker. In one embodiment, the amplitude of the incoming signal is reduced by an amount which is a function of the ratio of the amplitude of the incoming signal to the amplitude of the outgoing signal. Because loss is introduced into a distant speaker's transmit path rather than into his return path, it is possible for a near speaker to break into a conversation before the distant speaker has concluded. Further, since the loss provided is a function of the relative volumes of both speakers with respect to one another, the total loss introduced into the system is minimized.