Method and apparatus for detecting a compatible phantom powered device using common mode signaling

A method for providing a compatible communications device with a signal indicating that phantom power should be supplied to a connected data terminal equipment (DTE) device, said method comprising:

• receiving a detection signal over a first pair of conductors;
• coupling said first pair of conductors across a first transformer winding, said first transformer winding including a first center tap;
• extracting a signal at said first center tap;
• coupling an identity network between said first center tap and a second center tap of a second transformer winding;
• generating a response signal by applying said extracted signal to an input of said identity network;
• and
• transmitting said response signal over a second pair of conductors by applying an output of said identity network to said second center tap and coupling said second pair of conductors across said second transformer winding, said second center tap being a center tap of said second transformer winding.

An apparatus for providing a compatible communications device with a signal indicating that phantom power should be supplied to a connected data terminal equipment (DTE) device, said apparatus comprising:

• means for receiving a detection signal over a first pair of conductors;
• means for coupling said first pair of conductors across a first transformer winding, said first transformer winding including a first center tap;
• means for extracting a signal at said first center tap;
• means for coupling an identity network between said first center tap and a second center tap of a second transformer winding;
• means for generating a response signal by applying said extracted signal to an input of said identity network;
• and
• means for transmitting said response signal over a second pair of conductors by applying an output of said identity network to said second center tap and coupling said second pair of conductors across said second transformer winding, said second center tap being a center tap of said second transformer winding first winding of said second transformer.