Blog · Field Notes
Working guides from the manufacturer's side of the catalogue: standards, budgets, distances and the faults that fill maintenance logs.
Core size, wavelength, reach and cost — the single-mode vs multimode decision for Ethernet links, with the reach figures from real converter datasheets.
15.4W, 30W, 60W, 90W — what the three PoE standards actually deliver at the device, how classes and negotiation work, and which devices belong on which standard.
One device or twelve? Cost, cabling, management and failure domains compared — and the simple count that decides between a PoE switch and a shelf of injectors.
A standalone converter and an SFP module in a switch port do the same physics. The differences — management, power, spares, cost per link — decide which belongs where.
Why Ethernet stops at 100 metres, what long-distance PoE trades to reach 250m, and when extenders or fiber are the correct engineering instead.
Per-port watts are marketing; total budget is physics. How to sum device draw, add headroom, account for seasons and extenders — with a worked 24-camera example.
Port count, power budget, management tier, distance and environment — the PoE switch buying checklist in the order that actually decides the purchase.
Dead port, camera rebooting at night, link up but no power, intermittent drops — a field order for diagnosing PoE faults from the switch outward.
Temperature, surge, rings, mounting and power input — the industrial switch checklist that separates specified hardware from marketing adjectives.
Inside a PoE port: the signature detection, class negotiation and power delivery sequence — and why a PoE port never harms a non-PoE device.