A backplane is a printed circuit board that connect several connectors in parallel to each other, so that each pin of the connectors is connected to the same pins of all the other connectors.
It is used as a backbone to connect several PCB cards together to make up a complete system.
One popular early computer system that used this approach was called the S-100 bus because the connectors that where used had one hundred pins.
Some computers like the apple ][ and the IBM-PC integrated an internal backplane for expansion cards.
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