Fetron

The Fetron was a range of solid-state, plug-compatible replacements for vacuum tubes (valves).

Fetrons were manufactured by Teledyne Semiconductor from 1967; primarily as a low-maintenance and low-power swap-in to replace vacuum tubes, which were becoming increasingly obsolete and difficult to source with the widespread use of solid-state electronics. They were used in large numbers in telephone exchanges.{{cite web |last1=Storr |first1=Phil |url=http://www.philipstorr.id.au/radio/eleven/fetron.htm |accessdate=26 June 2016 |title=The Fetron |archive-date=2 March 2016 |archive-url=https://web.archive.org/web/20160302152133/http://philipstorr.id.au/radio/eleven/fetron.htm |url-status=dead }}{{cite web |last1=Palix |first1=Olivier |url=http://www.radiomuseum.org/tubes/tube_tr1011.html |website=Radiomuseum |accessdate=26 June 2016 |title=TR1011}} Vacuum tubes use significant amounts of power to maintain operating temperature, and large installations had substantial air-conditioning requirements; replacing them with fetrons was expected to reduce cooling and maintenance costs.{{cite book |title=FETRON solid state vacuum tube replacement |date=1973 |publisher=Teledyne Semiconductor |url=http://hrsasa.asn.au/docs/Fetron.pdf |accessdate=26 June 2016 |archive-date=27 February 2016 |archive-url=https://web.archive.org/web/20160227184512/http://hrsasa.asn.au/docs/Fetron.pdf |url-status=dead }}

A typical fetron consisted of a cascode configured pair of JFETs, some simple RC networks to control the device characteristics, and a fuse. The device was mounted in a metal tube with a base that has the same pin-out as the vacuum tube that it replaced.