Eurotherm Controls Inc. and Barber-Colman, Leesburg, VA, has published a 12-p guide on selecting solid state contactors and SCR power controllers for the control of heaters and other electrical loads up to 1800 Amps. The guide includes general information on the characteristics of different load types, good application practices, and a variety of formulas (i.e. how to calculate power, voltage, and current).