In article ,
"DoN. Nichols" wrote:

On 2010-01-10, Brian Lawson wrote:
On 10 Jan 2010 23:23:50 GMT, "DoN. Nichols"
wrote:

3N21


Hey DoN,

http://www.americanmicrosemi.com/information/spec/?ss_pn=3N21

O.K. Germanium means that I have given the wrong part number.
It was a silicon device. I wonder what those 3N devices were, how they
earned the leading 3 instead of 2. Transitron used it as a count of
junctions (e.g. one less than the number of leads.

The xNyy pattern is from a JAN standard, if I recall. I think that the
x is one less than the number of terminals, the then assumption being
that one must have at least two terminals. I don't think that the
number of junctions was considered, the intent being to treat the device
as a black box.

I would have guessed that 3N21 was an optocoupler, or a SCR with all
four layers connected. However, it seems to be an obsolete transistor
type made by Sylvania and Western Electric:
http://homepages.nildram.co.uk/~wylie/wanted.htm. However, it turns
out to be a Germanium switching transistor:
http://www.datasheetarchive.com/3N21-datasheet.html.

Joe Gwinn