Should the interconnect wire for smoke alarms read 120v?
Thank you all for comments. I was able to figure out the problem. Apparently the smoke alarm is polarity sensitive. Because of a wire change in the associated junction box, standard USA black and white was changed to British blue and brown. The brown is supposed to be connected to the black and white to blue, but they were reversed. Correcting this solved the problem. Now when the alarm is in &quot;alarm mode&quot; (test) it sends 18V on the red wire to the other alarms. and NOT have a constant 120V