[ntp:questions] SNTP server + ntpd 4.2.4 client
david at ex.djwhome.demon.co.uk.invalid
Tue Mar 18 18:28:22 UTC 2008
> Just looked it up. A bit bizarre-- power over the ethernet? The ethernet
> has no power supply capability. Do you mean that you have to supply the
> device with 60V running on one of the unused ethernet cable lines? Sounds
> noisy to me.
I believe it is a relatively new, but very real, standard. The power is
transmitted as a phantom between two pairs. In one variation, they are
the pairs used for normal, 10baseT. I gather one reason is that there
are exemptions in electrical codes for ELV power feeds as part of
datacommunication systems, whereas a normal feed would require a
formally qualified (not just competent) electrician.
The feed is 48V DC. I'm not 100% sure that counts as ELV, but it is the
same as most analogue telephone systems.
The apparent source specification is IEE 802.3-2005, although I haven't
gone to source.
As the power is common mode with respect to the signals, the noise
should not be excessive.
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