re: IP Phones over Ethernet, a clarification and then some
In message # 7056 uplinked I spoke about the IP Phone's need for power. I should have added that this is not a problem for conventional phones because they are powered by either the PBX or the Central Office via talk battery on the same twisted pair, or adjunct pairs, which are designed into the phone system in use. When an Ethernet link is used to support IP voice at an enterprise user's desktop, however, no such such form of battery over twisted pair is routinely supplied. Therefore, the need for an expedient through what was termed a phantom circuit power connection is being considered, instead.
In clarifying this, I stated:
"Well, this is not exactly the full personification of phantomry, but that's what the voip-in-the-enterprise guys are calling it today. FWIW"
I should have taken it a few steps further. A point that I should have made is that this form of powering through center-tap connections on the line side of the isolation coil is most commonly referred to as simplex wiring, or using simplexed battery and ground connections on the center-taps.
This is also the manner in which metallic DDS circuits and metallic T1 lines derive power from the central office and field repeaters: They do it through simplex connections via the center-taps on interface transformers.
The netheads probably discovered the term "phantom" and became enamored with it, or so I surmised in any event. It would follow, then, or it appears to me from a standpoint a posteriori, that they then chose to use the term "phantom" instead of "simplex."
And that's okay too, because we all come from a place called Geddalong University. Right? And so it goes.
FAC |
