Unusual UHN Behavior


As many of you know, I have an addressable silent Knight IFP-50 System. I replaced the notification appliances in the basement with a Siemens UHN-S-17 today that’s setup up for 4 wire operation and when I pulled a pull station, the horn NAC (NAC 1) started sounding in a 60 BPM pulse instead of the programmed code 3. I replaced the UHN with a 4903 tested it and the system did Code 3. Any explanations?

Upon further inspection, I discovered I forgot to cut one of the jumpers, I went ahead and cut it and now it works as it should