Thanks for the info, Zuse is fascinating. Z3 is very impressive, telephone relays were much more reliable than the valves used in Bletchley's Collosus by Tommy

Thanks for the info, Zuse is fascinating. Z3 is very impressive, telephone relays were much more reliable than the valves used in Bletchley's Collosus by Tommy Flowers. Failing valves prevented Collosus working until Flowers showed valves failed when powered off and so Collosus ran without cessation. Wonder why Flower's didn't use relays, he was a telephone engineer so was familiar with them.