DC Phantom
Simple DC signalling can be achieved on a telecommunications line in a similar way to phantom powering of microphones. A switch connected to the transformer centre-tap at one end of the line can operate a similarly connected relay at the other end. The return path is through the ground connection. This arrangement can be used for remotely controlling equipment.
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Famous quotes containing the word phantom:
“The first revolt is against the supreme tyranny of theology, of the phantom of God. As long as we have a master in heaven, we will be slaves on earth.”
—Mikhail Bakunin (1814–1876)