I still have my yellow by one, slightly modified jack end
Like this is what I use
https://rover.ebay.com/rover/0/0/0?mpre=https%3A%2F%2Fwww.ebay.co.uk%2Fulk%2Fitm%2F254245653828
Wireless ones better yeah? Like Honeywell hkc , do texe do a wireless smoke?
I mean wireless with built in sounder of course so can act independently , not that it can take the place of a proper fire alarm