[AusNOG] Question about hardware spec for a DC

[Bob Purdon]

> Avoid that auto power-transfer stuff in rack if you can. Those devices
> are best used only for low end boxes like NTU's/etc with which you can
> only ever install/utilise a single box at a time.

I'd agree - I've seen a few brands of transfer switches fail.  Relays 
welded shut that only become apparent during a switch, and one solid 
state unit that vaporised itself internally.

It's arguable if such an automatic transfer switch actually improves 
reliability at all, since now you've got two single points of failure in 
series (the ATS, and the device it's providing power to).

With cheap NTU's, there are certainly units out there that provide power 
redundancy as an option.  One I used a few years back could be fed with 
a DC plugpack as the optional second source (in addition to the internal 
power supply).