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Rick Wartzok came up with this old device used on the railroad for numerically addressing trains over shared radio frequencies. We converted it to a door lock. Here I remembered the device and built this solid model to illustrate its operational essentials.
My college friend Charlie Stewart found pictures of Rick and myself standing in front of our Dial-a-Door. This triggered the renewed interest in the device. I included Charlie's photos in the model.
In 2008 I found the original device and revived it for my friends at DorkbotPDX. website 