Storage Technology Corporation

Bell Telephone Laboratories

Patrick A Vachon

Peter G Ruether

Donald Gifford Hill

Theras Gordon Lewis

John Francis O'Neill

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. Data is determined to be present when the energy level of the high frequency components exceeds a multiple of the energy level of the low frequency components, and when the energy of the low frequency components is less than a maximum threshold and when the energy level of the high frequency components is greater than a minimum threshold and when the incoming wave has no slope all occurring simultaneously for a preselected period of time.

Data detection circuit for a TASI system

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. The gain of the controlled gain circuit is increased or decreased if the received test signal is outside of the acceptable range.

Centralized automatic gain control circuit

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.

Echo suppressor circuit

A time division switching system is disclosed having a plurality of telephone line circuits and common control circuits for switching calls over a time division communication bus. Ringing loop current detectors are shared by groups of the line circuits for detecting call answer signals during active ringing on a call and for controlling the line circuits to interrupt, or trip, the ringing upon a called party answer. Each group of the line circuits is permanently connected to a ringing current supply via an individual one of the loop current detectors. Each line circuit includes ringing control circuitry operated and released by the common control circuits for connecting ringing current to a called line during an active ringing interval and for disconnecting it during a silent interval of the ringing cycle. The circuitry is responsive to a detection of a called station answer signal by the shared loop current detector for immediately tripping ringing. Apparatus is also provided in the circuitry for sensing answer signals during the silent intervals and for generating switchhook status signals during both the silent and active ringing intervals.

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Arvada, CO, United States of America

Patrick A Vachon