Two Interlinked Smoke alarms are showing 24v between interlink connection and earth or neutral. They are sounding with no apparant cause - could this 24v on interlink wiring be causes it? The 24v is present on wiring even with smokes not connected
Are you using the black conductor as the interlink? If so then it's side by side with the brown conductor IIRC which you should have as the line conductor. What you're probably seeing is capacitive coupling from the line conductor.
When I next connect 230v interlinked detectors I'll measure voltage between the line and interlink to see if I see a similar voltage.