Hardware prerequisites

For this chapter, you're going to need several pieces of hardware:

1. First, you'll need a USB device that supports microphone in and speaker out. These are available at most online electronics outlets. One such device is shown next:
   
2. Then, you'll need a microphone that can plug into the USB device. Again, these are available at most online electronics outlets. Here is an example:
   
   
3. Finally, you'll need a powered speaker that can plug into the USB device. When you get the speaker, make sure it is powered. Your board will generally not be able to drive a passive speaker with enough power for these applications. This can either be internal battery power, or it can be powered via a USB. Here is a picture of such a device:
   
   

Fortunately, these devices are very inexpensive and are widely available. You'll need to get these before you...