May 2006, Issue 190

ARM-Based Modern Answering Machine
Philips ARM Design Contest 2005 First Prize

Just a few months before the end of the twentieth century, I bought my last telephone answering machine. Although it was a nice-looking brand-name system, I discovered a number of problems as soon as I started using it at home. The first problem was that the machine used an aggressive voice compression algorithm to reduce the size of the voice memory. This compression had a nasty effect on the quality of the recorded voice content. Another problem was that the machine had a cumbersome user interface that used voice prompts. I could check messages remotely, but I had to deal with the horrible voice prompts. The configuration was kept only if the answering machine was fitted with a fresh 9-V battery. Finally, I found the machine’s memory to be extremely limited. As a result, I had to check my messages frequently when I was traveling.

I built The Active Mansion Telephone Answering Machine (TAM-TAM) to solve all of these problems (see Photo 1). I didn’t replace the original answering machine’s poorly designed user interface with a better one. I avoided the issue altogether by editing a configuration file on a PC featuring a clear display, a keyboard, and text editing software. The configuration file is stored on a flash memory card that also stores all of my incoming messages. The system runs a small web server that displays a list of pending messages. I can retrieve the messages via the Internet.

In this article, I’ll explain how to build a similar answering system around a Philips LPC2138 microcontroller. Before I describe the circuitry, let’s take a look at the system’s basic modes of operation.