In Reply to: Ultra-sonic plans wanred, please. posted by Richard on 10/26/00 at 11:37 AM:
Greetings. I have just noticed your query and remembered that I had seen a circuit somewhere so I searched my own archives for it. The circuit is named "Ultrasonic Pest Repeller" and appeared in an early "Radio-Electronics" magazine (now defunct).
It uses a 556 chip configured to operate as a swept HF oscillator over a 25 to 65 KHz range and driving a Radio Shack piezo tweeter. If you still require something I would be happy to scan the page and E-Mail it to you.
I have not built this circuit, so cannot make any qualified report on its performance but it looks as if it might do your job.
Let me know if you want a copy.
Brian Snell (email@example.com)