From the field
Commercial security blog
The questions that come up once somebody is actually specifying a system, or has inherited one and is trying to work out what they have. Written from the installer’s side. Newest first.
In this section
Five posts
How long do security cameras keep footage?
Why there is no standard retention period, and what decides how many days a recorder holds.
What ONVIF does and does not guarantee
The gap between ONVIF conformance and “ONVIF compatible” on a datasheet.
The PoE power budget, and why it bites when you add cameras
What the PoE power budget is, and why adding cameras sometimes means a new switch.
NVR, VMS or DVR: what is actually recording your cameras
The three kinds of recorder, which one you are probably running, and what each one answers.
Fisheye or multi-sensor: choosing by what the view has to prove
Two ways to cover a wide space from one position, and how each one fails.
Where else to look
What is on the rest of the site
This section is deliberately narrow. Anything that belongs on a page about a specific discipline, a specific kind of building or a specific regulation is written there instead, because that is where a buyer looks for it and because two pages competing for one question serves nobody.
Federal procurement rules are under compliance, sourced burglary, false alarm and shrink figures under statistics, and the cost and comparison questions under buying guides. The interactive versions — a Section 889 checker, storage and power calculators, a cable run check — are under tools, and printable checklists under resources. The technical detail for each discipline is under commercial services, arranged by building type under industries, and by the problem you are trying to solve under use cases.
Two boundaries, as on every page here. We work on commercial premises only and not on private residences. And we do not hold a C-10 or a C-16, so we do not work on fire alarm systems; that is coordinated with your own licensed fire alarm contractor.