Early models of Shimano's STI brifters were only designed for use with double chainwheels.

The Erickson Gizzmo was an aftermarket cam device that permitted a double type front STI shifter to work with a triple crank.

The normal position had the lever facing down, and the STI brifter worked as a normal double, using the middle and large chainring.

When you flipped the lever up, the cam moved and gave extra slack to the cable, permitting access to the granny gear .