wanting to take a poll on how you are doing block occupancy. TWIN-T and derivatives Infrared optical optical [non infrared] reed switch i am thinking of applying an automated block control on the N scale layout [10x10 around the room shelf layout] and am wondering how happy people are with this. this is a 2 cab controlled layout [ok, 3, but i am not counting the yard] traffic is generally one direction, but that is from habit mostly. a simple way to visualize this layout is to draw three circles. outside circle touches the middle circle at one place only [double slip] middle circle touches the inner circle in one place only [facing turnouts] inner circle does not touch outside circle. in practice, the inner and middle circles come together to go across a drop bridge to allow you to get into the room. the outer circle is a helix and loop for the hidden yard section. yes, i have read many kalmbach books on this, and have been a subscriber to MRR since about 1979. these books generally don't mention any pitfalls people experience in actual application. thanks to everyone for the support!