Nobili cellular automata

Von Neumann specifically excluded the use of states dedicated to the crossing of signal.

The confluent state is altered, so that it acts as a signal crossing organ if exactly two signal paths are incident (they enter and leave the confluent state), or acts as a memory organ if only inputs exist.

The benefit of these alterations to the state set of von Neumann cellular automata is that signal crossing is greatly eased, configurations are slightly smaller than the corresponding configuration of von Neumann cellular automata, and the computational throughput is increased.

Due to the substantially reduced size (as compared with any of the vNCA crossing organs), self-replicating machines are much more compact in NCA.

One of these (the electronic method) is to create a loop of OTS cells with an excited pulse travelling around it.