Editing PED keyswitch

{{infobox dswitch
| image name          = Philips keyswitch -- top.jpg
| manufacturer        = [[PED]]
| product code        = 
| switch type         = Tactile
| force               = 
| introduced          = 
| discontinued        = 
| keycap mount        = Proprietary hollow square mount
| switch mount        = [[Plate mount]]
| patents             = [http://www.google.com/patents/EP0043618A1 EP0043618A1] (1981)
| inventor            = Laurence Harry Finlayson
}}

'''PED keyswitch''' is a series of metal contact switches allegedly manufactured by [[PED]]<ref name="PED" /> and patented by [[Philips]]. Designed to support centre illumination, it has only been seen in its non-illuminated form.

==Description==
The switch is plate-mounted, and has a very plain upper shell. There are no markings of any kind visible. The black shell contains a white [[slider]] with a large, square mount that takes a smaller square shaft within the [[keycap]].

The switches have two solder points, and two fixing pins in opposite corners.

Unlike with [[Hi-Tek Series 725]], the contacts do not close when the slider is removed. The contacts are closed under pressure by a funnel within the slider, and the separator bar in the slider holds the contacts apart simply to prevent inadvertent closing such as from impact. The terminals are identical, and the contact prisms are arranged at 45°, which means that they meet at right angles without needing to have opposing contacts with 0° and 90° angles.

The overall height is around 16.3 mm. Height above the mounting plate is around 9.3 mm, with around 6 mm below the plate. The switch is around 15.6 mm square at its widest point. Total travel is difficult to measure, but it is somewhere around 3.2 to 3.5 mm.

The switch is plate mount, but it also features two fixing pins, in opposite corners of the base.

The return spring is around 13.7 mm long with five inner turns, 9.4 mm outer diameter, 8.6 mm inner diameter, and 0.4 mm gauge.

==Keyfeel==
Because the contacts are pressed together by the slider, the feel is distinctly non-linear, but not tactile in the normally understood sense. The travel starts out linear, up to where the slider starts to press the contacts together; from here on, the switch is noticeably stiffer. The patent specifically describes how the switch design generates tactility, but the feel is not what one would normally classify as a tactile feel, and the effect is comparatively weak.

==Keyboards==
*[[Acorn BBC Microcomputer]]

==Gallery==
The switches depicted below were sourced from a BBC Micro.

<gallery widths=250 heights=187>
File:PED keyswitch -- keycaps.jpg                         | Comptec Philips-mount keycaps from a BBC Micro
File:BBC Micro Type 3 -- front view.jpg                   | BBC Micro Type 3 keyboard showing the Philips switches
File:Philips keyswitch -- top angled.jpg                  | Top view
File:Philips keyswitch -- side.jpg                        | Side view
File:Philips keyswitch -- rear.jpg                        | Rear view
</gallery>

===Disassembly===
<gallery widths=250 heights=187>
File:Philips keyswitch -- opening.jpg                     | Opening the switch with a screwdriver
File:Philips keyswitch -- top partially removed.jpg       | Top partially released
File:Philips keyswitch -- opened.jpg                      | Switch opened
File:Philips keyswitch -- opened, top view.jpg            | Opened, top view; notice how the contacts remain open with the slider removed
File:Philips keyswitch -- side view of contacts.jpg       | Side view of contacts
File:Philips keyswitch -- base.jpg                        | Base
File:Philips keyswitch -- base plug partially removed.jpg | Base plug partially remove
File:Philips keyswitch -- base plug removed.jpg           | Base plug removed
File:Philips keyswitch -- contact assembly.jpg            | Contact assembly
File:Philips keyswitch -- symmetrical contacts.jpg        | Symmetrical contacts
File:Philips keyswitch -- terminals and contacts.jpg      | Terminals with contact prisms; notice how the 45° angles allow for duplicate parts
File:Philips keyswitch -- slider bottom.jpg               | Slider, seen from below
File:Philips keyswitch -- slider operation.jpg            | Slider operation (slider in place with switch top absent)
File:Philips keyswitch -- contacts engaged, 1.jpg         | Contacts engaged
File:Philips keyswitch -- contacts engaged, 2.jpg         | Contacts engaged
File:Philips keyswitch -- disassembled, top views.jpg     | Full disassembly, bottom views
File:Philips keyswitch -- disassembled, bottom views.jpg  | Full disassembly, top views
</gallery>

==References==
<references>
<ref name="PED">BBC Micro Mailing List — [http://mdfs.net/Archive/BBCMicro/2005/09/14/012246.htm Subject: Interesting DRAM catalogue]</ref>
</references>

[[Category:PED switches]]
[[Category:Tactile switches]]
[[Category:Metal contact switches]]
[[Category:List of all keyboard switches]]