|The Heathkit story
The Breadboard Circuit Design Trainer ET-3100 came on the market in 1976. There was also a pre-assembled version ETW-3100. Several other Heathkit products could be bought pre-assembled and many of them, but not all, had the "W" in the type designation. The ET-3100 / ETW-3100 was then replaced by the ET-3600 / ETW-3600 in the early 90's. The ET-3100 was a product designed for educational purposes and that was what the Heathkit Educational Systems (HES) was fouded to do. Heathkit Educational Systems of today is still making this kind of products. The today's counterpart to ET-3100 is the ETS-3600 (or EWS-3600 as pre-assembled). My ET-3100 (or rather ETW-3100) is an OEM version made for Esselte and was used in schools in Sweden. I remember using them my self in school in the late 70's. The Original ET-3100 was in blue color but the OEM versions came in several different colors.