Along with the Xl/Xc coupled interference and the stored Capacitive charges from Xl/Xc coupling - already covered by members in this thread, there is another item which carries the term "Phantom" in it's description.
"Phantom Power" (may also be mistakenly reffered to as "Phantom Voltage", or "Phantom Current").
This is an intentionally designed scenario, which "carries" power to a certain device, via the "Signal" or "Data" wires that carry the devices data/signal to some type of processing device.
In a simple example, a Microphone and Audio Power Amplifier for the lead singer of a Rock Band make a great scenario!
The singer uses a 600 Ohm "Active" Microphone. The Microphone's internal Transducer will drive a signal out which is "Hotter" than a normal passive signal.
The Amplifier places a low power DC current on the Signal Line cable used to connect the Mic to the Amp.
The output sound signal from the Mic to the Amp is, of course, an envelope of AC frequencies.
The DC "Phantom Power" drives the "Active Pickup" (so to say) in the Microphone - thus delivering a much hotter signal to the Amp.
Some other examples include Active Guitar Pickups, "Carrier-Current" control / interfacing, some LAN hubs, various control equipment, not to mention POTS (Plain Old Telephone Systems).
Just wanted to point this out!
Scott s.e.t.
