What electrical part is this?

My teacher wants me to help him look for a certain electrical part. This certain part can be plugged into a breadboard, and has two different voltage inputs. ( two leads for 6 volts and two leads for 9 volts) He also said that this peice functions as a digital switch between two systems with different... show more My teacher wants me to help him look for a certain electrical part. This certain part can be plugged into a breadboard, and has two different voltage inputs. ( two leads for 6 volts and two leads for 9 volts) He also said that this peice functions as a digital switch between two systems with different voltages.
Here is a rough a sketch that he drew out and tried to explain to me: http://tinypic.com/r/v3ix5g/7

thanks for your help guys!
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