The MT8843 Calling Number Identification Circuit 2 (CNIC2) is a low power CMOS integrated circuit intended for receiving physical layer signals transmitted according to BT (British Telecom) SIN227 & SIN242, CTA (Cable TV Association) TW/ P&E/312 and Bellcore TR-NWT-000030 & SR-TSV002476 specifications. The CNIC2 provides all the features and functions offered by Mitel's MT8841 (CNIC), including 1200 baud BELL 202 and CCITT V.23 FSK demodulation. The 3-wire serial FSK interface provided by CNIC has been enhanced to operate in two modes. The first mode is the CNIC compatible mode whereby data transfer is initiated by the device. The new, second mode allows a microcontroller to extract 8-bit data words from the device. Furthermore, CNIC2 offers Idle State Tone Alert Signal and line reversal detection capability for BT's CLIP, ring burst detection for CTA's CLIP, and ring detection for Bellcore's CID.