What is BS 8243?

BS 8243 is the British standard for designing and installing alarm systems so that activations can be confirmed, in order to reduce false alarms. It is the standard behind the confirmed-activation requirement that police response depends on.

Where BS EN 50131 covers the system and EN 50136 covers the signalling, BS 8243 covers the logic that decides whether an activation looks real: how detectors are combined, sequenced and timed so that a single stray signal is not reported as an intrusion.

Its relevance to you is that it is the reason detector coverage and layout matter for police response. A system that cannot generate a confirmed activation cannot get a confirmed-activation police response, regardless of how good the monitoring contract is.

If police response is a requirement, say so before the survey, so the design accounts for it from the beginning rather than needing extra detectors afterwards.