Levers in a factory can be frobbed. Using a lever sends TurnOn to LockMe links. Trying to frob a locked lever will send TurnOn to ErrorOutput links.
One lever should control the cauldron, and another controls the mold. Each lever has a FnordLock associated with it. The cauldron lever links to the lock for the mold lever with a LockMe link. The mold lever locks the cauldron lever’s lock. The mold also has a LockMe link to the cauldron lever’s lock. Both levers link to an alarmlite with ErrorOutput.