The Red Box Detection Circuit can be used for a number of applications, specifically triggering household appliances or tone detection for security purposes. The original article was printed in 2600 Magazine and it is available here as well.



  • Original article in .PDF format (8 pages, no data sheets)
  • Original article in .PDF format (34 pages, including data sheets of relevant ICs)
  • Original article in Microsoft Word format (no schematic)
  • Schematic of circuit in PostScript file (included in .PDF files above)
  • BUG FIX: A GND connection is missing from the schematic, and proper detection will not work without it. On the right side of U2 (MX105A), components C8, C9, C10, R5, R6, R7 are all connected together. This connection needs to be pulled to GND.




    Last update occurred on 10/2/97 at 11:52pm



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