![Replacing 4 wire Smoke and CO detector connected to Alarm System - DoItYourself.com Community Forums Replacing 4 wire Smoke and CO detector connected to Alarm System - DoItYourself.com Community Forums](https://www.doityourself.com/forum/attachments/electronic-home-security-systems-alarms-devices/91599d1521213895-replacing-4-wire-smoke-co-detector-connected-alarm-system-2200.jpg)
Replacing 4 wire Smoke and CO detector connected to Alarm System - DoItYourself.com Community Forums
![4-Wire Smoke Detector with Relay Output YT142|Professional Conventional and Intelligent Fire Alarm System|CFT Fire Alarms 4-Wire Smoke Detector with Relay Output YT142|Professional Conventional and Intelligent Fire Alarm System|CFT Fire Alarms](http://www.cftfirealarms.com/images/20140307172758.jpg)
4-Wire Smoke Detector with Relay Output YT142|Professional Conventional and Intelligent Fire Alarm System|CFT Fire Alarms
ECO1000 Conventional Relay Base | Smoke Detectors | Sensors | Smoke Detectors | Honeywell Building Solutions
![2-wire or 4-wire? I have older smoke alarms series hardwired to a legacy alarm system (since removed). I want to replace them, but am stumped on if this is a 2-wire or 2-wire or 4-wire? I have older smoke alarms series hardwired to a legacy alarm system (since removed). I want to replace them, but am stumped on if this is a 2-wire or](https://external-preview.redd.it/jaQ2bN4oct6pFs1yySlDVUonrpseXcvj1jG-ctDTFQo.jpg?auto=webp&s=1e74cc6dccb27055af4d175f6b6c8b595160ef6f)