Abstract: A walkie-talkie device applies a continuous tone-coded squelch system (CTCSS) to control signal transmission. The walkie-talkie device has an analog-to-digital converter, a digital signal processor, and a digital-to-analog converter. The signal processing method includes using the analog-to-digital converter to convert a first analog signal into a first digital signal, using the digital signal processor to handle a CTCSS tone related to the first digital signal for generating a second digital signal, and using the digital-to-analog converter to convert the second digital signal into a second analog signal. The walkie-talkie device uses the CTCSS tone to discriminate a required speech signal from other speech signals transmitted by the same physical channel.

Abstract: A method for detecting a tone signal having a predetermined tone frequency includes receiving an analog communication signal, using a sampling frequency to convert the analog communication signal into a digital communication signal, selecting a plurality of signal sectors corresponding to a predetermined frequency range of the digital communication signal where the predetermined tone frequency agrees with the predetermined frequency range, and using the number of samples of each signal sector to determine whether the analog communication signal contains the tone signal.

Abstract: A walkie-talkie device applies a continuous tone-coded squelch system (CTCSS) to control signal transmission. The walkie-talkie device has an analog-to-digital converter, a digital signal processor, and a digital-to-analog converter. The signal processing method includes using the analog-to-digital converter to convert a first analog signal into a first digital signal, using the digital signal processor to handle a CTCSS tone related to the first digital signal for generating a second digital signal, and using the digital-to-analog converter to convert the second digital signal into a second analog signal. The walkie-talkie device uses the CTCSS tone to discriminate a required speech signal from other speech signals transmitted by the same physical channel.

Abstract: A method for detecting a tone signal having a predetermined tone frequency includes receiving an analog communication signal, using a sampling frequency to convert the analog communication signal into a digital communication signal, selecting a plurality of signal sectors corresponding to a predetermined frequency range of the digital communication signal where the predetermined tone frequency agrees with the predetermined frequency range, and using the number of samples of each signal sector to determine whether the analog communication signal contains the tone signal.

Abstract: A USB/UART converter connected between a DTE and a DCE is disclosed. The USB/UART converter comprises: a USB controller connected to a USB of the DTE, and a UART controller connected to the DCE and the USB controller. According to the present invention, the control signals for the DCE and the parameter settings for the UART controller are sent from the DTE through the USB controller in a control transfer mode. Then, the UART controller transfers the status signals through the USB controller to the DTE in an interrupt transfer mode after detecting the status signals coming from the DCE. Subsequently, the data can be transferred between the DTE and the DCE in an isochronous data transfer mode in response to the parameters.

Abstract: A method and apparatus for noise burst detection in a signal processor is provided. The method and apparatus is based on the zero-crossing rate (ZCR) of the received signal, which is defined as the number of times the magnitude of the received signal becomes zero during a specific counting period, to determine whether the received signal is a noise or a normal signal. The received signal is sampled at a specified sampling rate. Whether the signal waveform undergoes a zero-crossing is determined by comparing the polarity of the current sampled magnitude with that of the previous one. If the polarities are different, it indicates that the signal waveform has undergone a zero-crossing during the current sampling period; otherwise, it indicates that the signal waveform has not undergone a zero-crossing. The count of zero-crossing during each counting period is compared with a preset threshold value.

Abstract: A stand-alone, real-time voice recognition system, which converts an analog voice signal into serial digital signal, then preprocesses in parallel the digital signal to detect the end-point, and output fixed multi-order prediction coefficients. In this recognition system, these multi-order prediction coefficients are stored as the reference pattern in the training mode. In recognition mode, these multi-order prediction coefficients are adapted by dynamic time warping method, which is modified by a symmetric form. This symmetric form is implemented with a one-dimensional circular buffer for dynamic programming matching instead of the traditional two-dimensional buffer to save memory space. Finally, these adapted coefficients are compared with reference pattern to output the result of recognition.

Abstract: The present invention comprises an interpolation circuit for performing a linear interpolation operation for a voice synthesizer receiving a plurality of frames of voice data wherein each frame is subdivided into a plurality of sub frames with each sub frame being assigned with a predefined interpolation weighting factor. The interpolation circuit comprises an input port for receiving a plurality of sub frame voice data to be interpolated wherein said sub frame data are received in a predefined order. The interpolation circuit further includes a read-only-memory (ROM) for storing a plurality of multiplications of each of the plurality of sub frame voice data to each of the weighting factors and a read-only-memory (ROM) address generator capable of determining a address in ROM utilizing the sub frame voice data received from the input port and the predefined order of the frame and the sub frame thereof when the voice data is being received.

Abstract: A digital speech encoder and decoder have particular application to the field of 16 kbps digital communications. In the encoder, a speech signal is processed by a perceptual weighting filter, using a reconstructed speech signal, a reconstructed residual signal, and a set of filter tuning coefficients. A predictive signal, which is generated by a Short Term Predictive (STP) circuit, is subtracted from the signal outputted from the perceptual weighting filter. The difference signal is processed by a coder/decoder circuit to produce a reconstructed error signal, which is added to the predictive signal to form the reconstructed residual signal. A Linear Predictive Coding (LPC) circuit receives the reconstructed residual signal and develops the set of filter tuning coefficients. The set of filter tuning coefficients are outputted to the STP circuit, which also receives the reconstructed residual signal, and thereby generates the predictive signal.

Abstract: A baby cry recognizer is disclosed which includes an amplifier circuit for amplifying a received sound signal. In response to the amplified sound signal, a pulse generator circuit generates a pulse signal having zero crossings which are aligned with zero crossings of the amplified sound signal. The pulse signal, in turn, is inputted to a signal recognition circuit. The signal recognition circuit is capable of obtaining the zero crossing rate of the pulse signal during each of a preselected number of frames in a predetermined length time interval. The signal recognition circuit then determines if the zero crossing rate of the pulse signal, in more than a first threshold number of this preselected number of frames, is within a particular frequency range. The signal recognition circuit also determines if the zero crossing rate of the pulse signal over the entire time interval is greater than or equal to a second low threshold but less than or equal to a third high threshold.