On 23 Dec 2007 at 12:00, cctalk-request at classiccmp.org wrote: Not Schottky diodes, but *Shockley* diodes, a close relative of a diac. Genuine ones, circa late 1950's are very hard to find: http://semiconductormuseum.com/PhotoGallery/PhotoGallery_Shockley4E30. htm Schematic symbol looks like the number "4" with leads coming out of the top and bottom. Here's an application using some in an audio power amplifier: http://electronicdesign.com/Articles/Index.cfm?AD=1&ArticleID=3979 Sometimes also called a "transistor diode" and once intended to replace the 3-terminal transistor. Cheers, Chuck