Abstract: A signal discrimination circuit judges whether an input signal contains a control signal or not, the control signal having a specific frequency and a specific level for a specific time duration. The signal discrimination circuit includes a component power detection device for detecting the power of a component which is in the input signal and having the specific frequency and a level judging device for determining whether the power of the component is equal to or greater than a power reference value. Finally, a control signal judging device is included for determining that the input signal includes the control signal, when the level judging device judges that the power of the component is equal to or greater than the power reference value, continuously for the duration of a reference time.

Abstract: A stereophonic voice recording and playback device for stereophonically recording and reproducing voice signals, includes: an adding circuit for receiving a first channel analog voice signal and a second channel analog voice signal, performing orthogonal conversion of the respective analog voice signals, and adding the orthogonally converted signals; an Analog-to-Digital (A/D) converter for receiving the added signal from the adding circuit and converting the added signal to a digital signal; a compressing circuit for receiving the digital signal from the A/D converter and compressing the digital signal; a memory circuit for storing the compressed digital signal; and an expanding circuit for reading out the digital signal from the memory circuit and reproducing a stereophonic signal.

Abstract: In a signal reproducing device for reproducing voice signals from vector-quantized coded data, transferred or recorded coded data is extracted one by one, and the coded data extracted are given as initial values to a recurrence equation to generate a pattern composed of a predetermined number of data for every initial value. The thus generated patterns are sequentially output as reproduction data.

Abstract: A DTMF signal judging apparatus includes a first power calculator, and second power calculator and a judging apparatus. The first power calculator calculates the overall power of an input signal or the power of the input signal outside the DTMF frequency band. The second power calculator calculates the power in the DTMF frequency band; or more specifically, calculates the power in both the higher and lower frequency band portions of the DTMF frequency band. The judging apparatus then compares the output from the first and second calculators, and determines whether the input signal is a DTMF signal based on the comparison.

Abstract: A recording/reproducing apparatus for recording and reproducing an audio signal. The apparatus includes an external memory which can be mounted in and dismounted from the apparatus at will, and an internal buffer memory for temporarily storing the audio data. In the apparatus, a detection circuit detects the exchange of the external memory, and produces an output signal when the external memory is exchanged into a new external memory. In response to the output signal, an audio data transfer circuit transfers the audio data stored in the internal memory into the newly mounted external memory, thereby avoiding interruption of the recording during the exchange of the external memory.

Abstract: A DTMF signal judging apparatus includes a first power calculator, and second power calculator and a judging apparatus. The first power calculator calculates the overall power of an input signal or the power of the input signal outside the DTMF frequency band. The second power calculator calculates the power in the DTMF frequency band; or more specifically, calculates the power in both the higher and lower frequency band portions of the DTMF frequency band. The judging apparatus then compares the output from the first and second calculators, and determines whether the input signal is a DTMF signal based on the comparison.

Abstract: A voice reproducing device includes a data generator for sequentially providing digital data as an initial value to a recurrence equation and for generating a prescribed number of data with each given an initial value, a decoder for controlling the polarity of its output and the output time thereof in accordance with the data generated by the data generator and for outputting a pulse accordingly, and an analog integrating circuit for integrating the pulse output from the decoder.

Abstract: A DTMF signal receiving apparatus includes a DTMF signal receiver; and a DTMF signal judging circuit. The DTMF signal receiver includes an input section for receiving an input signal from an external apparatus; a plurality of first band-pass filters connected to the input section; a plurality of second band-pass filters connected to the input section; and an output section connected to the plurality of the first band-pass filters and the plurality of the second band-pass filters, for outputting a code based on a plurality of outputs from the plurality of the first band-pass filters and the plurality of the second band-pass filters.

Abstract: In a signal encoding device, a voice signal is divided into subsignals each comprising a predetermined number of successive samples, and data trains are generated by giving initial values to a recurrence equation. The generated data trains are divided into patterns each comprising the same number of samples as the predetermined number. The distance between each pattern produced by the pattern dividing unit and each of the subsignals are calculated. The pattern that provides the smallest distance with respect to each of the subsignals is identified, and the initial value set in the recurrence equation for generation of the data train that constitutes the pattern is output as coded data representing the respective subsignal.

Abstract: A signal discrimination circuit is provided with: a prediction circuit for releasing a prediction signal that is formed by making a linear prediction based on a previous input signal; a differential operation circuit for calculating the difference between the input signal and the prediction signal so as to release a predicted remainder; and a decision circuit for determining whether or not the degree of the variation of the predicted remainder from the zero level is maintained within a predetermined range. Therefore, even if a sound signal having a time-wise correlation and white noise having no time-wise correlation possess wide frequency components respectively, both of the signals are discriminated by the decision circuit based on the difference in the correlation. Thus, the signal discrimination circuit ensures an accurate discrimination between a control signal for a facsimile containing white noise and a sound signal.

Abstract: An IC card with a built-in voice synthesizing function is provided which includes a solid-state memory containing vector-quantized coded data, a pattern generating means for generating patterns each composed of a prescribed number of digital data by repeatedly performing calculations using a recurrence equation with initial values given by coded data read out of the solid-state memory, a converter circuit for limiting the band of each pattern generated by the pattern generating means and converting into an analog voice signal, and a gain control circuit for adjusting the gain of the analog voice signal output from the converter circuit on the basis of gain data read out of the solid-state memory.

Abstract: A noise generating device comprises a generator (1) including a shift register (1a) which performs shift operations to sequentially shift a bit in an input stage to a next higher significant stage. An exclusive-OR circuit (1b) performs exclusive-OR operations between a pair of bits from selected stages of the shift register and feeds back to the input stage of the shift register. A filter (2) receives the pseudo-random data and outputs an analog signal. The filter comprises an operational amplifier (2a). Respective outputs of the stages of the shift register are alternately applied to non-inverting and inverting inputs of the operational amplifier through respective resistors (R1, . . . ,R23).

Abstract: A phase shift angle detector for detecting a phase shift angle of a multiphase modulated signal includes a first multiplier coupled with a first low pass filter for producing a cosine wave signal having a phase which is a sum of a phase shift .phi.e and the modulated signal g(t), and a second multiplier coupled with a second low pass filter for producing a sine wave signal having a phase which is a sum of a phase shift .phi.e and the modulated signal g(t). A circuit is provided for calculating an inverse tangent using the cosine wave signal and the sine wave signal to produce a signal representing the pahse shift .phi.e.