tota

In advance thank you for your help! I work in a museum. We have 24 plasma screens on two floors showing 24 DVDs (running from 24 DVD players). All the DVD players are in a room in the basement. From the DVD machines to the plasma screens wires were run through the cement at the time of construction. (It is not possible to pull through new or additional wires.) I would like to have three different videos sent to each screen from 72 separate DVD players in the basement. And be able to choose between the three DVDs at any time by pressing an A/B/C switch near the screen. The wiring is not coax, but rather a single pair of copper video cables with a yellow RCA plug at the end. There are also two lines of speaker wire running from the DVD players in the basement to each plasma screen. Is there a devise that would alow me to run 3 DVDs on one pair of wires. What I am imagining is some how shifting the frequency of two of the DVD signals and then sending the two shifted signals plus one unshifted signal up one wire. Then before going through the A/B/C switch I would have a device that would shift the signals back and send one signal through each line of the switch and then to the plasma screen. Is their any economical way to do this? Or do you have a better idea? Thank you in advance for your help. Andy