Metal rectifier
A metal rectifier is an early type of semiconductor rectifier in which the semiconductor is copper oxide or selenium. They were used to convert alternating current to direct current. They were often used in devices such as radios and battery chargers. Westinghouse Electric was a major manufacturer of these rectifiers since the late 1920s.
In some countries the term "metal rectifier" is applied to all such devices. In other countries the term "metal rectifier" normally refers to copper-oxide types, and "selenium rectifier" to selenium-iron types.
Other websites
change- Rectifier used as an AM-demodulator Archived 2014-09-04 at the Wayback Machine
- Cougar Electronics - example of "legacy" selenium rectifier manufacturer
- The Copper Oxide Rectifier This document discusses the history of the copper oxide rectifier, and, in particular, the use of Chilean copper in its manufacture; the thallium catastrophe that befell the manufacture of selenium rectifiers is also discussed.
Wikimedia Commons has media related to Copper-oxide rectifiers.