Work for profile; I built and developed these units around 1977. They're still operational. I still have my divy checks from Esterline and a lot more documentation. http://electricalequipmentplus.com/products/scientific-columbus-esterline-watthour The Gem unit has lasted many years and is now known as the GemStar. I'm currently watching a stinkie penny stock for possible patent violations. Now part of Ametek http://www.ametekpower.com/power-transducers/scientific-columbus-analog-transducers.aspx The unit I gave birth to now evolves into the GemStar 2 http://www.ametekpower.com/Meters/JEMStar-High-Accuracy-Revenue-Meter.aspx GEMStar 2 http://www.ametekpower.com/Meters/JEMStar-II-High-Accuracy-Meter.aspx This will be part of my new professional profile along with the history of the Compu-Key 20