Abstract: A system and method having automatic selection of impedance values for matching against unknown line impedances. The method stores an expected set of desired return loss measurements at given frequencies and matches the calculated set against the actual measured return losses to arrive at a close approximation of the line impedance. The system is then adjusted based upon this determined close approximation. The starting point for the stored set are standard models established for each network. In situations where the actual varies greatly from the predicted, a different model is selected and the expected scores for that model are used.

Abstract: A system and a method for echo suppression which use two or more microphones for beamforming of an echo signal corresponding to an incoming speech signal that is output by a loudspeaker. The outputs of the microphones are appropriately filtered and then linearly combined to cancel the echo signal, even if the incoming speech signal has been non-linearly distorted. Also, the microphones may be selectively positioned or pointed to allow the linear cancellation of ambient noise.

Abstract: A speakerphone having echo suppression is provided. The speakerphone has an audio control system comprising a transmit path, a receive path, a pair of rectifiers for producing rectified signals indicative of the strength of the signals present on the receive path and the transmit path, respectively, and an analog-to-digital converter for generating digital samples of the rectified signals for further processing. The audio control system further includes a general use microprocessor. Samples of the rectified signals are taken periodically and processed to determine if the receive path or the transmit path should have control, or if the audio system should be in an idle state. If speech is detected on either channel, the samples are weighted depending on the current state of the audio system. The weighted samples are then analyzed to determine which path should have control.

Abstract: A circuit for sensing telephone line conditions, comprising: high impedance termination means across the telephone line; means for accumulating charge through the high impedance termination means; and electrical isolator means intermediate the means for accumulating charge and voltage detecting means.

Abstract: The present invention is related to a telecommunication system and method enabling a user to get access to any of automated call processing systems. The system comprises in combination a telephone line interface means adapted to provide function of a telephone set, a control means connected to the telephone line interface means, and adapted to constantly monitor the telephone line, analyze a call progress and a ring back tone signals and to switch automatically without human intervention from a pulse dialling mode to a DTMF dialling mode upon detection of a ring back signal validated by a central office. This system also includes a handset and keypad means connected to a telephone interface means and the control means. The central office processes calls in a pause dialling mode. The system enables the user to get access to automated call processing systems, the access to which is limited only to callers equipped with a DTMF telephones and central office base DTMF services.

Abstract: A method for detecting the presence of voice, single tone and dual tone signals compares a ratio r which equals the square of the maximum value of the received signal (A max) during a sampling period divided by a measure E of the energy to three different thresholds. If r is less than the first threshold (3) a single tone is indicated. If it is greater than the first but less than the second (5.2) a dual tone is indicated. If it is greater than the second, the received signal level is compared to the third threshold (-43 dB) and receipt of a voice signal is indicated if the level of the received signal exceeds this threshold.

Abstract: When there is an incoming call to a digital line and the digital line is to be connected to a digital terminal, a CPU connects the line and the terminal directly. When the digital line is to be connected to an analog individual line telephone or the like, the line and the terminal are connected via a level controller. The level controller shifts, to an appropriate level, the level of a voice signal represented by data received from the digital line, and the analog individual line telephone or the like connected to the extension receives the voice signal shifted to the appropriate level.