Abstract: A voice controlled voice-messaging systems permits manipulation of voice messages over the telephone without the need for keypressed commands. Manipulation includes playback of messages, deletion of messages, saving messages, and sending a new message to a recipient from a user-defined list. Access to the messaging system is by spoken password. Voice input also allows the following functions: enrollment of a spoken password; granting or refusing user access to the system based on verification of the user speaking a password; recognition of spoken utterances of "yes" and "no" in response to prompts by the VMS; recognition of "stop" to interrupt and stop a voice message during playback; enrollment of a spoken personal directory of names of potential message recipients; and recognition of names in the spoken personal directory.

Abstract: Reliable access to audio and facsimile message storage and retrieval systems is accomplished by employing a listening procedure to differentiate voice message clients from fax clients and, upon identifying a fax client, performing an extended listening procedure to differentiate between a sending fax client and a retrieving fax client. During the listening procedure, the system generates a ring tone, immediately after connecting the call, comparable in duration to that normally expected by a caller during a typical call attempt, thereby rendering the listening procedure transparent to a human caller. The masked listening procedure allows detection of standard calling fax machine, polling fax machines and accommodates a blind polling procedure for use with fax machines not equipped for standard call in polling. Blind polling is accomplished by monitoring a fax receiver in the system for a called station tone (CED) or if a CED tone is missed by the system, detection of V.21/V.

Abstract: An apparatus and method for echo cancellation in voice-messaging and voice-response systems, to enhance recognition of received DTMF and voice signals, comprising an efficient software echo canceller using adaptive digital filtering techniques. The voice messaging system includes analog telephone line interface modules which provide digitized voice data to a digital signal processor (DSP) chip. A transmit data line and a receive data line are each coupled to a cancel module with a cancel filter and an adapt/window module with an adaptive digital filter. The cancel filter causes echo cancellation on the receive data line; the adapt/window module monitors buffered transmit data in non-real time, without directly causing cancellation to occur, and selectively transfers an adjacent window of filter coefficients to the cancel filter under control of an adaptation control coupled to the adapt/window module.

Abstract: An automatic gain controller for a digitized audio signal, comprising a buffer with a plurality of subframes. Each subframe contains digitized data samples of the signal, the subframes including at least one future subframe and a current subframe. Signal processing means (such as a DSP) is coupled to the memory for controlling gain of the audio signal represented by the current subframe in the buffer. The signal processing means includes means to control gain of the data samples using a stored program for computing a plurality of mean signal level values from the plurality of subframes, each mean signal level value in the plurality corresponding to one of the subframes. The program includes means for causing decay of gain on the signal represented by the current subframe when a first set of the mean values are each below a low threshold signal level.

Abstract: In a digital messaging system (10), an apparatus (37) and method for determining whether a DTMF (Dual Tone Multi Frequency) digit is present on an input signal (11,12). A heuristics engine (37) performs a series of tests on the input signal (11,12) using a set of parameters that are stored in a RAM (38). There is one parameter for each of a set of input signal (11,12) characteristics and for each of a set of operating modes of the digital messaging system (10). All of the parameters are configurable. The configurability allows for the use of non-standard telephone equipment (13,14) and minimizes deleterious effects such as talkoff. The tests are from the set of sets comprising an absolute magnitude test, a frequency deviation test, a twist test, an echo test, a consistency test, and a temporal test.

Abstract: An all digital feature based pattern recognition tone detection system distinguishes one or more tones from speech or other background noise and provides extremely reliable, low cost DTMF tone detection. The system includes a digital signal processing system which uses a modified PARCOR signal analysis technique to efficiently calculate inverse filter coefficients defining in functional form a smoothed LPC spectrum from a received frame of digital pulse code data. A Fourier transform provides high resolution evaluation of the LPC data at frequencies of interest to permit evaluation of the spectral response in accordance with known features of an expected tone signal.