Oak Series 475
Series 475 from Oak appears to be a lower-profile derivative of the tall Series 400 switches. The newer series incorporated the following changes:
- Reduction in overall height
- The metal blade plunger was replaced by a cruciform-mount plastic plunger
- Plate retention clips are moulded into the shell
Details on Series 475 are scarce. The earliest advertisement discovered to date for Series 475 is from December 1973, in Electronic Design magazine. As with Series 400, Series 475 was produced on automated assembly line.
The Series 475 switch shell has “U. S. PAT. 3,708,635” moulded into it, indicating that it is covered by the same patent as Series 400.
The photos below are from Deepak Kandepet, and show the variant with SPST configuration and a dummy lug:
Additional photos show that the plunger can be either dark brown (or black or grey: it is not clear) or red.
Only the following details are known:
|Rated lifetime||20 million cycles|
The switches are described as having crossbar-wiping, self-cleaning gold alloy contacts. The 1977 advertisement also notes that they have “Sealed PC terminations”.
The 1977 advertisement gives the following configurations:
- SPST (NO and NC)
- DPST (NO and NC)
- SPDT non-shorting (implying break before make)
- Alternate action
- SPST with dummy lug (depicted below)
All material was scanned by Bitsavers unless otherwise noted.
- Oak keyboard switch advertisement, Electronic Design, Vol. 21 No. 20, September 27 1973
- Oak keyboard switch advertisement, Electronic Design, Vol. 22 No. 18, September 1 1974, pages 12–13
- Oak Series 475 advertisement, Computer Design, May 1977, page 178