Alps elastic contact types
Elastic contact switches (previously known as “integrated dome” switches) use conductive rubber domes as part of the contact mechanism. The term “integrated dome” arose from these switches being discrete units that each contained a single rubber dome.
Elastic contact switches originally (or at least previously) used series names beginning “KE”, which was later amended to “SKE” (see series names). It appears that Alps eventually ran out of SKE* series names, and extended the range into SKP*. The only known keyboard type in this latter group is SKPA. In Alps literature, SKE* and SKP* are listed together as one collective group, which falls within the tact switch classification.
There is no conclusive list of elastic contact types; the list below shows all types discovered to date. Photos of the keyboard switch types are mine; all other photos are misappropriated stock illustrations. Some types are confirmed to exist, but have no available photos.
Older types are assumed to have three-letter series names unless confirmed as being included in the renaming exercise. Newer series (SKPA onwards) are assumed to have four-letter series names.
|Yes||Non-keyboard pushbutton||This is an elastic contact type, misreported as metal contact in the 2000/2001 European catalogue; KEC10901 was used in the Yamaha SU700 alongside Hirose Cherry MX1A-0NNN|
|KED¹||Yes||Keyboard switch||Used in the Roland TR-808 (KED10903 and KED10001); the former was also used in the Boss DR-55|
|Yes||6.0mm Square Type (Snap-in)|
|KEH¹||Yes||Keyboard switch||Used in some TRS-80 machines, as well as the Roland MC-4 (KEH4A006) and JUNO-6 and JUNO-60 (KEH10003)|
|KEJ||Yes||Non-keyboard pushbutton²||Type KEJ10901 was used in the Roland JUNO-60|
|SKEL||Yes||Unknown||Part SKELAJA010 exists; SKELAK was used in the Roland MKS-20|
|SKEQ||Yes||SKEQFA was used in the Roland MC-500 Mk II|
|(S)KEV||Yes||Exposed dome switch||Part SKEVAA is used as the reset switch in the Sega Genesis II|
|(S)KEW||Yes||Keyboard switch (Alps keycap mount, plate mount, two-piece shell)||Series name is yet to be confirmed.|
|SKEY||Yes||Exposed dome switch||SKEYAG was used in the Yamaha RM1x|
|SKPA||Yes||Keyboard switch (Alps keycap mount, plate mount, one-piece shell)||White is SKPAAA, and black may be SKPAAB (no details found with that part number)|
|SKPD||Yes||7.8mm Square Type (Radial) SKPD Series|
|SKPE||Yes||6.6×6.3mm Low-profile and Heavy Operation Type TACT Switch||Seemingly discontinued|
|SKPF||Yes||Long-travel Type with High Operation Force (Snap-in)|
|SKPG||Yes||High Operation Force Type with 5.0mm Height (Surface Mount)|
|SKPH||Yes||Listed in the 1993 Alps catalogue|
|SKPL||Yes||6.45mm Diameter Low Contact Resistance Type with Round Terminal (Radial)|
|SKPM||Yes||Low Contact Resistance Type (Surface Mount)|
|SKPR||Yes||High Operation Force, Low Contact Resistance Type (Surface Mount)|
|SKPS||Yes||Contact Resistance Type (Surface Mount Type)|
Not all keyboard types have been formally identified. The PCB-mount keyboard types in particular remain fully unidentified. Patents for the enter key stabiliser seen on the Zenith Supersport show that the PCB-mount design goes back as far as August 1985, the filing date of the Japanese patent. The US patent is 4771146.
This is plate-mount, and the shell can be opened for maintenance unlike the earlier KED Series. In all known instances, the plunger is black. Typically the plunger is cruciform mount, but blade mount also exists in a General 2017PD printing calculator found from late 1983 or early 1984. Key travel in that example was measured as 3.5 mm.
The identity of semi-integrated dome has yet to be determined. Several switches are similar, but not close enough.
SKPD has two terminals instead of four, which seems to rule it out.
SKEY series is a candidate, but no SKEY types have been sighted with the correct dome shape.
Like SKEY, SKEVAA is close, but both types have legs that protrude slightly from the sides of the switch. The switches in the ICL One Per Desk seem to have recessed legs that are covered over by switch. SKEVAA has the recess in the centre of the dome, but it is a much deeper recess than that of the switches in the ICL computer.