def main(self, x):
        """ Transposed FIR structure """
        self.acc[0] = x * self.TAPS[-1]
        for i in range(1, len(self.acc)):
            self.acc[i] = self.acc[i - 1] + x * self.TAPS[len(self.TAPS) - 1 - i]

        self.out = self.acc[-1]
        return self.out