Flow through butterfly backpane

A backpane for receiving a plurality of printed circuit boards, said backpane comprising:

• a board having a length, width and height,
• aperture means positioned along said length for receiving electrical connectors,
• ventilation means positioned along said length for allowing air to flow from one side of said board to another,
• said ventilation means comprising a plurality of holes,
• said holes being positioned above and below said aperture means, and
• wherein board has a plurality of connectors positioned in each of said aperture means,
• each of said connectors having a plurality of contacts connected thereto, and
• said contacts having different lengths, and
• wherein said contacts are of three different lengths.