Futaba linear switch

Futaba linear switch
Manufacturer	Futaba, Sejin Electron
Family	Futaba linear switch
Switch type	Linear
Sense method	Metal leaf
Keycap mount	Custom cruciform
Switch mount	Plate mount, PCB mount

Futaba linear switch is a provisional term for a family of linear plate-mount switches typically with cylindrical shells. The term was selected to contrast the later "Futaba clicky switch", part of Futaba MA series.

Description

Futaba linear switches all use stout, cylindrical legs that are threaded at the top and screw in. The switch terminals are separate internal parts that the legs make contact with inside the switch.

Most types are plate mount, and have a square-top cylindrical shell with truncated sides. In these types, the shell contains the whole switch, and the internal parts are held in by a base plug. The base plug for larger switches is secured solely by the legs, while the small type also has a clip on the base to secure it in addition to the legs.

A final known type has a square or rectangular cross section to the shell and is sealed shut.

The number of parts between Futaba switches varies. MD series "complicated linear" momentary switches comprises sixteen parts. The sealed switches share the short legs with MD series so are likely to have the same internals. MR and ML series switches have simplified internals of only nine and seven parts respectively.

Futaba linear switches have a lower travel than many other switches; travel ranges from around 2.7 to 3 mm across the switch range.

George Risk versions

Futaba linear switches were resold by George Risk as GRI products. MD series was resold as GRI KBM series, and ML series was resold as GRI KBM-LP.

Variants

Futaba MD series

Main article: Futaba MD series

MD series "complicated linear" is the most common series, found in a number of forms including momentary and alternate action, upright and angled keystem, short and tall keystem, and illuminated. The single confirmed part number is MD-4PCS.^[1] Different switch colour combinations exist, and these colours have not yet been decoded.

The switch has a non-uniform cruciform slider approximately 4.0 mm by 4.7 mm, with 1.2 mm wide arms, taking a 4 mm deep keycap stem. The distance between the plate and PCB is 12.7 mm.

The switch comprises 16 parts in total.

Futaba MR series

Main article: Futaba MR-6C series

The simplified variant of the switch is physically compatible with the complicated variant, but uses only 9 parts: the complex contact assembly is replaced with bare contacts. The contacts remain distinct from the terminals, as with the complicated designs.

MR-6C series has been shown to contain the only type ever encountered; no documented evidence for MR types beyond MR-6C has yet been discovered. MR-6C itself is known only from a few types of equipment.

The switch actuates at mid travel, at around 60 cN.

Futaba ML series

Main article: Futaba ML series

ML series represents a reduced-size version of MR series. Differences include the plate retention clips being attached to the base plug instead of the main shell, and the pins being offset towards the front of the switch.

Keycap mount compatibility is maintained with the larger switches.