A method and apparatus to receive and demodulate call related information, e.g., Caller ID information, in an audio codec placed on the line side and powered by current drawn from the telephone line. The audio codec includes a 1st order SIGMA/DELTA A/D converter to digitize the signal from the telephone line with SIGMA/DELTA modulation. The 1st order SIGMA/DELTA A/D converter may be a scaleable component capable of alternative operation in a 2nd order. The SIGMA/DELTA encoded digitized signal is digitally processed by a DSP including an amplifier module, a digital filter, a limit/slice module, and an FSK decoder to receive and output the call related information. Placement of the audio codec on the line side and the scaleable SIGMA/DELTA A/D converter provides significantly reduced power requirements for the audio codec, thus allowing operation from power derived from the telephone line. In another embodiment, to further reduce power consumption of the audio codec, the 1st order SIGMA/DELTA A/D converter is sampled at a slower rate than is conventional, e.g., by first dividing or otherwise providing a slower sampling clock.