Left panel controls the movement and the amount of the spawner. 1 two or 3 blocks, forward, backwards and stop, and two eject buttons. The right panel controls what block type to spawn.

This allows the player to call the spawner and drop off some blocks. You see now three 2 by 1 blocks being dropped off.

The two tracks with the spawner and the two raising platforms at the end to control the spawners. The controls in the wall call the spawner and allow you to spawn 1, 2 or 3 blocks at once.

Player Spawn exit at the left, ramp in the middle, and block spawn controls at the right.