Caller ID: an opportunity to teach DSP-based demodulation

This paper discusses one of our real-time DSP course´s most popular projects, demodulating a telephone´s caller ID signal. We describe the use of a modified telephone coupler to allow students to access the caller ID signal and then discuss a number of the DSP methods and techniques that are required to successfully demodulate, decode, and display the caller ID information. This project has been exceedingly well received by both our undergraduate and graduate students and represents a DSP-based solution to a real world communications problem that every student has seen in use. This project involves almost every aspect of realtime signal processing implementation, but is not so overwhelming in scope that it cannot be completed in a reasonable amount of time.