How to make a contraction door in the mini world?

Practice of elevator door in mini world:

First put a four-grid-high geocentric door frame with two grids and three grids in the middle.

Put a slider in the upper right corner with the plus sign pointing forward.

Put the markers in the upper and lower positions.

Fill the board and put the squares on it.

Place the circuit as shown.

Set the geocentric door frame to block the circuit line.

Put the switch in two positions as shown below.