The MT8841 Calling Number Identification Circuit (CNIC) is a CMOS integrated circuit providing an interface to various calling line information delivery services that utilize 1200 baud BELL 202 or CCITT V.23 FSK voiceband data transmission schemes. The CNIC receives and demodulates the signal and outputs data into a simple 3-wire serial interface. Typically, the FSK modulated data containing information on the calling line is sent before alerting the called party or during the silent interval between the first and second ring using either CCITT V.23 recommendations or Bell 202 specifications. The CNIC accepts and demodulates both CCITT V.23 and BELL 202 signals. Along with serial data and clock, the CNIC provides a data ready signal to indicate the reception of every 8-bit character sent from the Central Office. The received data can be processed externally by a microcontroller, stored in memory, or displayed as is, depending on the application.