Repeat steps 2 to 4 for all of your outdated BRK alarms. We advocate changing all alarms within the system together to maintain the best possible system Procedure; failing to take action could compromise interlink functionality. The SBBRKSM easichange® kit replaces the discontinued BRK 660MBX optical and 670MBX ionisation smoke https://www.firesense.co.uk/type/addressable-fire-system/addressable-fire-alarm-control-panels/