0:00 Intro 0:53 The FACOM 128B 1:53 History of relay computers 5:16 Trip to Mt Fuji and Fujitsu's Numazu plant 6:12 Detailed look at the FACOM 128B 10:33 Simple example: 3+3, deciphering the lights 12:49 Calculating square root of 2 13:44 Crossbar mechanical memory 17:07 Large calculation demo 21:30 Maintenance 22:34 FACOM and the rise of Fujitsu 23:16 More footage of the 128B in action This FACOM 128B was designed in 1958 and built in 1959, and is part of Fujitsu's (and Japan's) first commercial computers series. It uses over 5,000 relays, and still works to this day! Samtec and Fujitsu arranged for me to see this very special machine in action during a recent visit to Japan.   Many thanks to Fujitsu: Mayumi Funamura Yoshio Takahashi Tadao Hamada and Samtec: Yasuo Sasaki Brian Vicich for making the visit possible. Special thanks to Robert Woodhead for providing precious technical information. Some relevant links: Outstanding CHM video on the early machines mentioned here: https://www.youtube.com/watch?v=qundvme1Tik Nice list of amateur relay computer projects: https://hackaday.io/project/11798-relay-based-projects Viewer @aljawad solves the same problem on a HP-15C pocket calculator from 25 years later: https://www.youtube.com/watch?v=dyL5CozJsZU Our sponsor for PCBs: https://www.pcbway.com/ Support the team on Patreon: https://www.patreon.com/curiousmarc Merch on Teespring: https://teespring.com/stores/curiousmarcs-store Learn more on companion site: https://www.curiousmarc.com/ Contact info: null