What and how to fix this problem? INVREP Smoke detector. Change out SD355 to a SD365IV. SD355 is discontinued.
Hi @Safeandsecure,
It’s unclear if you’re really asking a question, or telling us the answer to a problem… But I’ll bite a bit:
INVREP will come up on Honeywell panels when a detector is unresponsive. This could mean that the detector head bad, taken down, or a cut wire. Assuming the device is up and the wire back to the system is good, it’s an indication that the detector head would need to be replaced.
As mentioned in your post, the current replacement options for an SD355 would be the SD365 if Light Speed is supported. If an older panel that only supports CLIP protocol, then SD365IV is required, and of course a bit more expensive as well. If an SD365 will work on your system, that will be the cheapest replacement option.
The 9050UD is clip only, so the SD365-IV is the only option.
As for you @Safeandsecure, if the detector works but throws a trouble, check the sticker on the back of it and see where it was made. The majority of Honeywell Ivory detectors manufactured in India are “fake”, and they don’t work with CLIP. My friend Fire-Lite457 bought an ivory heat detector for his Notifier system, and it didn’t work on CLIP. It was made in India. When you purchase Honeywell detectors, always make sure they were made in Mexico as the Mexican detectors are much better and don’t have any largely known issues compared to the Indian ones.
Hope this helps, let me know if you need more help! 
Whoops, good catch on me. Thanks!
I didn’t know Honeywell detectors where also made in India
Lol yeah they are, they suck though. They either have terrible QC, or the Indian ivory versions are only for aesthetics rather than functionality regarding support for the CLIP protocol.