Editing Alternate action (section)

==Construction==
===Notch wheel===
[[File:Cherry MX Lock -- slider with locking wheel.jpg|250px|thumb|Notch wheel in [[Cherry MX Lock]]]]

This method is described in [http://www.google.com/patents/US3770923 US patent 3770923], filed in 1972 by Cherry. A wheel with three pairs of teeth is affixed to the slider by a post, and this wheel is free to rotate. A lug within the switch rotates this wheel every time the slider is depressed, and on alternate cycles, the wheel engages with a second lug within the switch. The space between each pair of teeth is right-angled, and after engaging with the upper lug, holds the slider down. When the slider is pressed again, the wheel is rotated further, and as it encounters the upper lug again, it is given another push. This rotary approach imparts no noticeable force, and thus leaves the switch completely linear.

===Notch bar===
[[File:Omron B3G-S Lock -- position 1.jpg|250px|thumb|Notch bar in [[Omron B3G-S Lock]]]]

The notch bar approach used by [[Omron B3G-S Lock]] is a development of Cherry's method; [https://www.google.com/patents/US4495391 US patent 4495391] was filed for it in 1982. Instead of a wheel with three pairs of teeth, a bar is used instead. Where the total rotation per lock-unlock cycle is was 120° with Cherry's notch wheel, it is 180° with Omron's notch bar.

===Cam track===
The vast majority of alternate action switches use a cam track: a roughly heart-shaped linear cam track. A follower arm traverses this track, and the dip in the centre top captures the follower and thereby the slider. Ramps within this track ensure that the follower always proceeds the correct way around the track. To keep the follower pressed against the track and ensure that it engages the ramps, some source of pressure is required. In [[Alps SKFL Lock]], the follower pin sits in front of a leaf spring, while [[RAFI full-travel key switch]] and [[SMK lock]] use a helical pressure spring. [[Alps SKCL Lock]] uses a flexible plastic arm as the follower, and resistance to flexing provides the pressure.

The cam track can be moulded into the slider, with the follower located in the switch (as used by Alps, SMK and Mitsumi), or the cam track can be placed in the switch, with a follower arm connected to the slider (as used by RAFI and Futaba).

Currently, Cherry and Omron are the only brands known to have opted for any method besides a cam track.

<gallery widths=250 heights=187>
File:Alps SKFL Lock -- slider with latch track.jpg                   | [[Alps SKFL Lock]] slider with cam track
File:Futaba-Lock-Upper.JPG                                           | Base of [[Futaba lock]] with stationary cam track insert
File:SMK lock -- lower side view.jpg                                 | The follower pin in [[SMK lock]] has its own slide-in module
File:Alps lock disassembled.jpg                                      | [[Alps SKCL Lock]] partially disassembled
File:RAFI RS 74 M SPDT latching -- slide block partially removed.jpg | [[RAFI RS 74 M SPDT latching]] slide block partially removed
</gallery>