< <> And (though no doubt I'll find I'm wrong when I look at those web pages <> I thought Z3 was a relay machine, not electronic. < <> [Distinction. Relay - switching is performed by moving parts of the <> circuit. Electronic, whether tubes or solid state, switching acts <> directly on the electrons (or holes), hence the term] Mechanical: man or motor powered, bars cams, wheels Electric: Relays, steppers, solonoids and contacts has logic tree. Electronic: uses active devices, tubes, transistors, ICs some types of diodes and neon filled tubes. Allison