Kidde CO Alarm Interconnect Signal
Here’s the signal trace for the Kidde KN-COSM-IBACA dusl smoke-co sensor interconnect when Carbon Monoxide (CO) is detected. The signal for CO is (presumably) 10100101 and it repeats every 5.9 seconds. In the interval it speaks out loud in English “carbon monoxide detected” or something like that. The fire signal is a constant +12 v, no 8 bit data. There is a hush signal code but I didn’t bother capturing it.
Here’s the 8-bit signal for CO – 10100101
Click on the images for full size view so you can see the timing information.