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Advanced Input Devices



Advanced Input Devices (AID)—now Advanced Input Systems (AIS)—is an American human–machine interface manufacturer based in Coeur d’Alene, Idaho and founded in 1978 by John Overby. In the computer keyboard market, their speciality was elastomer mat (rubber sheet) keyboards, which were introduced no later than 1984.

The best-known Advanced Input Devices keyboards are the two variants of IBM PCjr keyboard: the original “chiclet” type and the replacement conventional-keycap type. Both were standard elastomer mat types. Curiously, AID appear to have always used a PCB for the matrix circuit, rather than membranes. Being chosen by IBM to manufacture the PCjr keyboards was a major deal for Advanced Input Devices, increasing their annual revenue from $4 million to $15 million; as reported in the New York Times article “Advanced Input’s I.B.M. Coup” from 26th November 1983, sales were expected to double in the following year.

The NY Times article goes on to note that Advanced Input Devices was founded with a loan of “less than $50,000” by John Overby who claims that he started the company because he was “sick of the politics of a large company.” The “large company” in question is presumed to be Key Tronic, a former employer of not just Overby but numerous other Advanced Input Devices staff, and a business described in the article as “the keyboard industry giant with sales of $80.5 million last year”. Advanced Input Devices was located only 30 miles from Key Tronic. As of November 1983, their production output was 5,000 keyboards per day, making them second in line below Key Tronic themselves. Advanced Input Devices “produces virtually all its own components, and makes the tools and molds the plastics for each model”, according to the article.

Advanced Input Devices also shared production of at least one model of Compaq Enhanced Keyboard. While primarily known as a Key Tronic foam pad capacitive product, some of these were also produced by Advanced Input Devices using conductive rubber domes.


The official, trademarked series are PKD, MKD, MKE etc. The keyboards and keypads themselves tend to be marked with their UL models, known to range from AID-1 through AID-6. The exact correspondence between the AID models and the named series remains to be confirmed; there is no official correspodence, but it appears to serve as a useful way to identify series. The series names and their basic details have been provided directly by Advanced Input Systems.

PanelKey Dome (PKD)

This is a flat panel design, with stainless steel domes on a rigid PCB. This appears to correspond with AID-1.

MicroKey Dome (MKD)

This uses hinged plastic keys over stainless steel domes on a rigid PCB. A “Microprofile” keyboard, model MK 038-001, was advertised in Computer Design magazine in April 1981. Travel is only 0.400″ (1.52 mm). Bounce time is 2 ms. MCBF (mean cycles between failures) is given as 15 million. Possibly the MK type was renamed MKD to accommodate MKE. AID-2 appears to cover this type.

An eBay listing for an AID-2 keyboard almost identical to MK 038-001 appears to show that separate plungers exist below the keycaps.

MicroKey Elastomer (MKE)

These have an elastomer mat; reportedly they can have either rubber or plastic keycaps. It seems more likely that “rubber keycaps” simply denotes having the keys formed from the elastomer mat. Examples include:

Both examples are identified as “MKE” rather than by an AID number.

ErgoKey International (EKI)

EKI is the full-travel chiclet series. This appears to be what was used for the original IBM PCjr keyboard. EKI keyboards are intended for use with graphic overlays that fit around the keys. For example, there is a Microsoft Flight Simulator overlay for use with the PCjr keyboard. EKI could be seen in an August 1984 advertisement in Computer Design magazine. EKI keyboards provided a choice of 2 oz and 3 oz operating force and offered a 60 million cycle lifetime.

A few photographs of the inside of an original PCjr keyboard can be seen in the Register article IBM PCjr STRIPPED BARE: We tear down the machine Big Blue would rather you forgot.

There is a suggestion that EKI was developed at IBM’s behest specifically for the PCjr keyboard, giving Advanced Input Devices its first line of full-travel keyboards.

ErgoKey Truncated (EKT)

EKT appears to be a revision of EKI that offers conventional keycaps. In his Revised IBM PCjr keyboard review video, Chyros demonstrates that the replacement PCjr keyboard uses the same case as the chiclet version. EKI and EKT were advertised together in Computer Design magazine in August 1984 (as simply “EKI” and “EKT”), and appeared to share the same specifications.

EKT keyboards have the plunger guide shafts moulded into the top housing, just like most non-scissor rubber dome keyboards today. The later PCjr keyboard (as shown in the video) does not have discrete plungers: the rubber domes are operated directly by the keycaps. By comparison, the keyboards made for Tektronix have discrete plungers. Whether both types are EKT is not confirmed.

The following photos, from the Lake Michigan Computers website and used here with permission, show an AID-made Compaq Enhanced Keyboard, which is pictured on the cover of the Ergokey Series brochure:

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Front view of the plunger
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Top view of the plunger

EKT keyboards have distinctive plungers that should allow easy recognition. Typically the plunger will be white, but in this instance black was chosen.

EKT keyboards appear to correspond to AID-3.

ErgoKey Single station (EKS)

EKS keyboards use discrete plunger guide shaft modules fitted to a metal mounting plate. This method is more flexible and has a lower tooling cost than a fully-moulded top housing. EKS keyboards appear to correspond to AID-5.

AID codes

Many Advanced Input Devices keyboards are marked with an AID number as their model number. These numbers are so far known to span the range AID-1 to AID-6. These are not actual model numbers, but rather a lookup number for Advanced Input Devices’ UL file. The specific details of these codes is no longer available. Broadly these numbers correspond with keyboard series, but they refer to compliance profiles and ratings rather than any specific switch technology. The known types are as follows:

AID number Known series Type
AID-1 Panelkey Dome
AID-2 Microkey Dome
AID-3 Ergokey truncated
AID-4 Known AID-4 keyboards have all the keys moulded from a single rubber sheet, presumably to provide a fully sealed assembly. The series name is not yet known.
AID-5 Ergokey single station The AID-5 rating itself may be related to the use of a plate mounting; the Allen-Bradley 8520-MKBB front panel is AID-5 yet it has flat buttons instead of keyboard keycaps
AID-6 Suggested by Advanced Input Systems to be a separate rating (e.g. flammability) resulting from putting a PKD keyboard within an enclosure. There is only one known example, and the AID number has been manually recorded as or changed to “6” with a black marker pen, possibly AID-1 for the underlying PKD panel.


Very few patents are known for AID’s keyboard products.

Patent Title Filed Published Product
US 4523060 Combination keyboard 1983-11-17 1985-06-11 Appears to be PanelKey Dome
US 4618744 Rocker key elastomer dome keyboard 1985-04-29 1986-10-21 Appears to be MicroKey Elastomer (hinged plastic keys, over domes, over a PCB)
US 7557312 Keyboard assembly 2006-02-10 2009-07-07 Full-size keyboard


IBM PCjr keyboard

The November 1983 New York Times article “Advanced Input’s I.B.M. Coup” describes the then-upcoming PCjr keyboards as a “major departure” for Advanced Input Devices, suggesting that they were not in the full travel keyboard business until this time. Reportedly (according to other keyboard makers that IBM had approached at the time) the target price for the PCjr keyboard was an “unusually low” $15 to $20, which was not considered feasible by other manufacturers. Key Tronic were asking $25–30 for quality full-travel keyboards, while General Instrument wanted $18–19 each. Unfortunately IBM’s decision was a poor one, as the resulting keyboard was a substandard experience. The end result of this was a revised design with conventional keycaps, EKT, that is otherwise identical to EKI.

According to the NY Times article, the Advanced Input Devices keyboards are more energy efficient than the IBM Model F keyboard. The implication in the article is that all the matrix columns (or rows) are tied to a NAND or NOR gate that acts as an interrupt to indicate that a key is pressed and that the matrix should be scanned; this is how the BBC Microcomputer keyboard functions. As such, full continuous scanning is not required, although the BBC Micro keyboard does still require a multiplexer to connect one row at a time to the NAND gate, and there is no multiplexer in the PCjr keyboard. The Model F keyboard, being capacitive—just as with Key Tronic’s keyboards—requires continual scanning to detect keystrokes. As the PCjr keyboard supported infrared communication and could be powered from four AA cells, this low-power design presumably extended the battery life of the keyboard. Quite how it works remains unclear, however.

Detailed photographs of some of the circuitry can be found in the Deskthority forum topic IR PC keyboards: IBM and Quadram. From this, we can see that the PCjr keyboard contains the following complement of chips:

Part Quantity Purpose
M80C48-83 1 MCS-48 family microcontroller (8 kB ROM, 64 bytes RAM)
MC14011B 1 Quad dual-input NAND gate
MC14013B 1 Dual D-type flip-flop
MC14060B 1 14-stage binary counter
MC14068B 1 8-input NAND gate
MC74HC02 1 Quad dual-input NAND gate
MC74HC03 2 Quad dual-input NAND gate

The MC14068B 8-input NAND gate may well be the chip that initially detects keystrokes.


EKT-101 is a conventional 101-key keyboard, sold to various customers. The following photos, from the Lake Michigan Computers website and used here with permission, show a Ciba-Corning AID-3 keyboard. This is marked AID-3 rather than as an EKT-101, but it is essentially identical to keyboards marked as such, as can be seen from this unbranded example.

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AID label
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The chief difference with the example above, compared to most other EKT-101 keyboards, is that it uses a J-shape return key and single-unit backspace, but an identical Ciba-Corning EKT-101 keyboard was also produced. This latter example also has no clearly marked date code; potentially “572891” could indicate 1991 manufacture but there is little if any precedent for a six-digit date code.

This example uses discrete plungers together with moulded-in plunger slots.


The “Model” column in the table below refers to AID’s terminology, in how keyboard types were identified by their AID codes instead of their series names. The AID codes are taken from the products, while the series names are a guess based on the appearance of the keyboard.

The date code format is not yet known. However, the final two digits appear to indicate the year, e.g. 07697 indicates some point in time within 1997.

Only alphanumeric keyboards, or units containing an alphanumeric keyboard, are included in the table below. Various AID series were also used for control strips and panels with no data entry capability.

Keyboard Model Series Part Date Notes Reference
Unidentified miniature MKD? 9370-132 A 182 Virtually identical to MK 038-001 as advertised in April 1981 eBay
IBM PCjr type 2 EKT ~1984 The AID branding appears on the rubber dome sheet Deskthority
Silicon Graphics 9980991 ~1987 Plate-mounted Cherry MX switches Deskthority
Unclear Electrohome EKI Chip dates are not readable: photo too small Deskthority
Marquette Centra Cardiological keyboard EKT ~1988 Date is a guess from the Intel chip markings Deskthority
Unspecified panel AID-6 ? 9370-00725-301 10189 The label has been manually corrected to read “AID-6” eBay
Unspecified Tektronix AID-3 EKT ~1990 Deskthority
Unspecified RCA-like AID-1 PKD 9370-00038-504 C 24190 Identical layout and almost identical styling to an RCA VP601 keyboard (the typography is not an exact match) eBay; eBay; eBay
Unspecified MKD AID-2 MKD 9370-00093-517 3 14594 Ideal Machinery
ABB 168-key AID-5 EKS 9395-00208-001/V 03096 Twitter
Unspecified 83-key AID-5 EKS 9395-00309-001/4 07697 Amazon
Unspecified flat keyboard AID-1 PKD 9370-00792-101/H 10897 Caps lock uses an integrated LED; the arrow keys are in a non-inverted T stradding the function key row and the number row. eBay
Unspecified Honeywell control station AID-3 EKT 9395-00282-005 A 03499 eBay
Unspecified rubber sealed AID-4 ? 9372-00352-002/A 13302 eBay
Unspecified Honeywell control station AID-3 EKT 9395-00381-029/A 26911 eBay

Date codes and serial numbers

AID/AIS date codes are typically five digits long, and indicate the day of the year (zero-padded to three digits) followed by the last two digits of the year. For example, a date code of 13302 indicates the 133rd day of 2002. Serial numbers are specific to the date of manufacture, e.g. the first keyboard of each day will have a serial number of 1, scoped to the date of manufacture. This curious practice leads to many keyboards appearing to be early production or part of a limited production run, when this is not necessarily the case. A batch of very early MK or MKD keyboards have been found with date codes of “182”, suggesting January 1st 1982. This date would have been a holiday, and this format is presently anomalous and unexplained. This code could instead have represented January 1982 instead, or week 1 of January.

Many keyboards are marked with the code “CDA”; this simply indicates that the keyboard was manufactured in the Coeur d’Alene plant in Idaho. The other factories would have used different codes.


All documentation was provided by Bitsavers unless otherwise specified.