The following site contains description and schematic of another relay-based processor.

It was created in 1950s and can be used to demonstrate principles and architecture of processors.

Here is the description taken from the site: “Simon is a Harvard architecture machine constructed from relays. The program is executed directly from paper tape. In these regards it was behind the state-of-the-art as several electronic stored-program machines were under design or construction by the late 1940s. The main data registers and ALU are 2 bits wide, data input is via either the paper tape or 5 toggle switches, output is via 5 lamps.

As an educational instrument, Simon was directed more towards the electrical implementation of logic than towards programming. As such, and as a minimal machine, programmibility is rather limited. The one saving grace may be that the program can be quite long (limited only by paper tape handling), a feature that certainly would not have been feasible in an attempt to make an inexpensive stored-program machine at the time.”