# Instructor Guide for Week 2

The second week introduces*systems*as functions that map functions (signals) into functions (signals). Again, it should focus not on how the function is defined, but rather on what is the domain and range. Block diagrams are defined as a visual syntax for composing functions. Applications considered are DTMF signaling, modems, digital voice, and audio storage and retrieval. These all share the property that systems are required to convert domains of functions. For example, to transmit a digital signal through the telephone system, the digital signal has to be converted into a signal in the domain of the telephone system (i.e., a bandlimited audio signal).

### Problem session

- Appendix A, problems 4, 5, 6, 13, 14 (turned in in week1), 16 (Matlab)
- Chapter 1, problems 1, 4
- Sidebar on electrical power