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Eight articles on voice alarm systems, all by Nigel Williams: a five-part series on sizing Public Address Voice Alarm (PAVA) standby batteries to BS 5839-8:2023, the first two of a series on emergency communication in venues, and an explainer on 100 V line. Technical guides, testing advice and honest analysis, written for the people who maintain and manage these systems. No gate, no form, no follow-up call.

Battery series: sizing standby batteries to BS 5839-8:2023

Five parts, best read in order.

The page I almost turned. The BS 5839-8 battery clause behind our calculator. 16 July 2026.
Your next voice alarm battery quote should be smaller than your last. What the 2023 edition changed, and three questions to ask before you sign. 16 July 2026.
The worked example that doesn't work. The arithmetic error in BS 5839-8:2023 Annex C, traced term by term. 22 July 2026.
What battery manufacturers should publish, but do not. The 30-minute discharge figure the calculation needs, and who publishes it. 31 July 2026.
Peukert's law oversizes your voice alarm batteries. The number hidden in the usual equation, and the line at 20 Ah. 6 August 2026.

Still to come: the 1.25 ageing margin, and the data nobody publishes to support it.

Emergency communication in venues

Written for the people responsible for a venue rather than the people who install its systems.

Attention please: the two worst words to start an emergency announcement. The words that open almost every UK emergency announcement came bottom of eight in the study that ranked them. 6 August 2026.
Fire follows physics. An attacker reads your procedure.. Message libraries are built for fire, which never reads the plan. Why the emergency microphone is a venue's primary control, and who keeps it ready. 11 October 2026.

Still to come: the certificate measures the half of the chain with no person in it.

Explainers

100 V line explained: why the amplifier's power ends up in the loudspeaker, not the cable. Why 100 V line exists, worked through 20 m of Cat 5e: 40 % of the amplifier's power lost in the cable, or 0.4 % on 100 V line. 8 October 2026.

By question

Is my voice alarm battery quote too high? Part 2, then part 5, then the battery calculator.
How do you size standby batteries for a voice alarm? Part 1, part 3 and part 4.
What should an emergency announcement say? The venue article: five elements, an order, a reading age, a repetition rule and a speech rate.
Why do PA systems use 100 V line? 100 V line explained, with both worked examples.
Where are the clause references? In each article's "Where this comes from" table, and under Standards, in our own words.

In preparation

Six pieces, being written or brought up to date from their 2024 masters. Titles only.

The Noise Measurement That Shrinks a PAVA Quotation
How to test a PAVA loudspeaker circuit: seven checks for fire techs
Fault-finding loudspeaker circuits with the Zircle impedance meter
Three voice alarm tests every stadium should run
More loudspeakers won't fix the room
The No B.S. Guide to Speech Transmission Index (STI PA) for Fire Techs: a reference guide to the measurement method, for when a specification asks for it.

Five guides first published in 2024 are among these; until each returns, its old address brings you here. The calculators the articles refer to are under Tools.