PDF instructions for building a large mushroom interlocking. The signal box has been designed with great attention to detail. Inside there is a staircase that leads to the "bridge". The huge mechanics for setting the switches and signals are set up here. On the upper floor there is also a desk for office work and through the doors you get to one of 2 balconies, where you have an even better view. And the stepladder leads to the attic.