Storage Technology Corporation

Peter G Ruether

John Francis O'Neill

Patrick A Vachon

J Mark Elder

Disclosed is a centralized circuit for determining whether input signals from a plurality of channels are speech which includes memory means in which digital amplitude samples from each of the input channels are stored in real time. A control means then periodically retrieves the samples from the memory in a time faster than real time and produces a series of time compressed input signals which are compared with a variable threshold derived from a stored level for each channel. Moreover, means are disclosed for setting a new threshold whenever the time compressed input signals differs from the old level for a predetermined time, the new level thereafter being stored in place of the previously stored old level.

Speech detector circuit for a TASI system

Speech detector circuit with associated gain control for a tasi system

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 apparatus for and a method of complex signal generation and transmission having particular application in a time assigned speech interpolation or TASI system. Samples of the amplitudes of a plurality of signalling status and test signals are stored in a digital code in a digital memory. These samples are retrieved as needed without the need for a plurality of time base signal generating means. The signal to noise ratio of the signals to be transmitted is increased by statistically predicting the n equally likely amplitude ranges of the entire set of signals. Each character of the digital code employed identifies one of these ranges. The more likely occurring amplitudes are thus defined by more code characters than are the less likely amplitudes. Additionally, the signal to noise ratio of the entire set of signals is increased while minimizing the digital storage requirements of the system by the provision of a second digital memory for storing a single amplitude within each of the above-mentioned ranges. The samples stored in the first memory are used as index vectors which identify and select the single amplitudes stored in the second memory which are then transmitted to the receive side of a TASI system. Since the second memory is 2 x bits wide, while the index vectors are stored in a memory only X bits wide, digital storage requirements are minimized.

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Boulder, CO, United States of America

Peter G Ruether