ANSWERS: 2
  • They have a small contact under the paper that actually causes a small shortcircuit. When you open it the circiut closes, send enegy from a small battery to a tiny speaker and...tra la la la Happy birthday, .......
  • I first saw them selling 25 years ago; so the engineering is likely pretty simple..

Copyright 2018, Wired Ivy, LLC

Answerbag | Terms of Service | Privacy Policy