Patent ID: 6668057
Filing Date: 2003-12-23
Classification: H04M,H04Q

Abstract:
An apparatus for receiving and processing a tone signal generated by arbitrarily combining a plurality of reference frequencies, comprising:processing means for processing the reference frequencies so as to and a first reference value for each of the reference frequencies and a second reference value for each of the plurality of reference frequencies and calculate an arithmetic value at current time for each of the reference frequencies, the first reference value being calculated by multiplying the arithmetic value for each of the reference frequencies by a coefficient, which is held in said processing means, before a predetermined period which is n times of sampling periods, wherein n is an arbitrary natural number, the coefficient being determined in accordance with each of the reference frequencies, the second reference value being calculated by subtracting the arithmetic value for each of the reference frequencies from a current tone signal, which is held in said processing means, before 2 times of the predetermined periods, the arithmetic value being obtained by repeating processing of adding the first reference value and the second reference value a number of times equal to a number of samples corresponding to each of the plurality of reference frequencies; output value extraction means for extracting an output value equal to or larger than a predetermined threshold value from the arithmetic values for the respective reference frequencies, which are calculated by said processing means; and signal determination means for determining a type of the tone signal on the basis of at least two output values extracted by said output value extraction means.