Selenium rectifiers and their design

Selenium rectifiers are dry-plate rectifiers of the electronic type. The history of dry rectifiers began some 30 years ago with the advent of the copper-sulphide rectifier. In the early 20´s, the copper-oxide type came into common use, and during the past three years, selenium rectifiers have found wide application in American industry. Fundamentally, this third and latest type of rectifier is a continental development and has been manufactured in Europe within the International Telephone and Telegraph group of companies during most of the 1930´s. Sufficient experience was gained in the technique of manufacture, as well as in methods of design and in selection of applications, to warrant engineering statements as to their general usefulness and importance to industry.