O'Reilly logo

Computers as Components, 3rd Edition by Marilyn Wolf

Stay ahead with the world's most comprehensive technology and business learning platform.

With Safari, you learn the way you learn best. Get unlimited access to videos, live online training, learning paths, books, tutorials, and more.

Start Free Trial

No credit card required

6.10 Design Example: Telephone Answering Machine

In this section we design a digital telephone answering machine. The system will store messages in digital form rather than on an analog tape. To make life more interesting, we use a simple algorithm to compress the voice data so that we can make more efficient use of the limited amount of available memory.

6.10.1 Theory of Operation and Requirements

In addition to studying the compression algorithm, we also need to learn a little about the operation of telephone systems.

The compression scheme we will use is known as adaptive differential pulse code modulation (ADPCM). Despite the long name, the technique is relatively simple but can yield 2× compression ratios on voice data.

The ADPCM coding ...

With Safari, you learn the way you learn best. Get unlimited access to videos, live online training, learning paths, books, interactive tutorials, and more.

Start Free Trial

No credit card required