how can a phoneline have both ac & DC?

our phone lines have static, a friend told me to check to voltage (for ac to see if the cordless phone was the iussue) I check and the line has 110AC and about 52 DC. I unplugged the cordless phone and still get the ac voltage. most of the phone jack boxes show the dual voltage, but I have found one that only shows the DC, and no AC what so ever. How is this possible?

NachoMahma8 years ago
1) Using the wrong AC/DC setting will cause false readings. 2) Judging by your question, I'd have to say there's a good chance you are not taking proper measurements. 3) It is very possible to have DC and AC at the same time. Ever seen a remote camera that only has coax going to it (no power wires)? The camera is powered by DC on the coax and the video signal is superimposed on top of the DC. At the monitor end, the DC is "subtracted." 4) If you actually have 110VAC on your phone lines, when it is not ringing, then you have a problem.