How to generate an alert tone from a computer

I recently read a Code Project thread that got into a discussion about beeps, internal speakers and alerting the user. This reminded me of a story from a previous life...

It was the early 90s and I worked for a company that provided software to E-911 dispatch centers. There was a machine room with racks of computers and then the actual dispatch center which only had user I/O devices. The monitors and keyboards were run through special extension hardware that allowed VGA, keyboard, mouse, serial and parallel ports to be removed from the computer by a fair distance. It seems like the system would drive them up to 100 feet away, but my memory could be faulty. In any case, we had all these extension boxes scattered throughout the center but all the built-in computer speakers were back in the server room.

A feature of the software allowed dispatchers to place calls in a pending queue. This was for low priority calls that didn't have resources available for immediate dispatch. After a timeout, things in the queue would start escalating. First they'd change color. Then they'd start flashing. The Chief wanted the next level to be an audible alert. And, with this being the fire department, audible alert didn't mean a simple "beep." It needed to be impossible to ignore, klaxon-loud and obnoxious. And of course there wasn't any budget for any significant hardware. I thought about it on the drive home and had an idea as I fell asleep.

The next morning I stopped by Radio Shack and picked up a $10 monophonic amplifier. Something simple. (Amazingly, I just searched for it and they still sell the same model 20+ years later, albeit at a slightly higher price.) I also got a 1/8" patch cord and power adapter. When I got to the dispatch center, I cut off one end of the patch cord and connected the leads to the ground and transmit pins on an RS-232 connector on one of the extension boxes. Then I plugged in the amplifier, turned the volume down low, created a short text file with some random characters and cat'ed it to the appropriate /dev/tty port. An earful of noise rewarded my efforts.

Now I knew my idea would work. Playing around with different repeating character sequences gave different patterns. Changing the baud rate would change the frequency. Eventually I came up with a combination that worked pretty well. It was loud, obnoxious and impossible to ignore. The Chief loved it. And it cost less than $20 and an hour or two of work.

About me and this blog

Hi. I'm Harley and I'm a software developer. I'm also a lot of other things, but the focus of this site is about software development and this aspect of who I am. I grew up in the graphics arts industry; my Dad and Granddad both owned and managed print shops. I got into software by working on computer-driven typesetting equipment from there I started writing software to work with these devices. In this context I've been around and involved with computers since grade school.

I started programming a TRS-80 Model 1 while in Jr. High learning Basic and Z-80 assembler. From there I moved to Business Basic on a Data General Nova and C on an S-100/Z-80 based multi-user machine. Since the mid-90s I've primarily worked on desktop applications in the Windows environment.

The goal of this blog is to provide an place for my thoughts on the what's happening in the software development scene. They range from general development issues to technology specific things I work on.

Comments are welcome but I do moderate them. This is simply to keep things wholesome for general family viewing. By default, comments will be accepted. The few things that will cause a comment to be rejected are:

1. It is too long even though it may be well-written and make interesting points. It's supposed to be a comment, not an essay. If you have that much to say, write a blog article and backlink to me.

2. It is nasty, impolite or uses language that is unacceptable.

3. It includes a a link that has a typo or is broken in some other way.

4. It should have been sent as an e-mail since it is clearly addressed to me and does not appear to have been intended for other readers.

5. It is blatantly self-promotional. This does not mean it can't be self-promotional at all, but it should add some value over an above the marketing.

My e-mail is harley3 at pebley.org. I also twitter. And finally, I have a page that contains a list of my other blogs and some more general information about me.