/* Process the 8 frequency filters */
for (k = 0; k < NDTMFCOEFF; k++)
{
	/* Goertzel processing */
	sk = sk1 = sk2 = 0;
	for (n = 0; n < DTMF_NPOINTS; n++)
	{
	sk = DTMFsamples[n] + ((DTMFCoeff[k] * sk1) >> 15) - sk2;
	sk2 = sk1;
	sk1 = sk;
	}
	/* Prevent overflows */
	sk  >>= 1;
	sk2 >>= 1;
	/* compute |X(k)|**2 */
	power = ((sk * sk) >> AMP_BITS) -
	((((DTMFCoeff[k] * sk) >> 15) * sk2) >> AMP_BITS) +
	((sk2 * sk2) >> AMP_BITS);
	result = result >> 1;
	if (power > DTMF_TRESH)
	{
	result += 0x80;
	}
}