Dig a two deep trench connecting the redstone torches on each side of your piston set up.
Remove a block underneath the block that your redstone torches sit on. Do this on either side.
Place a redstone torch. You will see that the top redstone torch deactivates.
Dig three blocks out from the torch you just placed and run redstone wire to a third torch.
Connect these third torches with redstone wire as seen above. This will ensure the piston arrays communicate with each other when activated.