Apple Adjustable Keyboard
| Apple Adjustable Keyboard | |
|---|---|
 |
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| Apple Adjustable Keyboard M1242 with its separate keypad | |
| Manufacturer | Apple Computer, Inc. |
| Type | Ergonomic split keyboard |
| Interface | Apple Desktop Bus |
| Compatible | ADB-equipped Macintosh computers |
| Weight | 1005 g (keyboard), 372 g (keypad) |
| Model | M1242 |
The Apple Adjustable Keyboard (model M1242) was Apple's only split ergonomic keyboard. It is two halves hinged at the centre rear that swing apart horizontally, with the large space bar remaining in the centre, attached to the fixed base.[1] It shipped with removable wrist rests — one per side — and with a separate numeric keypad that has its own wrist rest and carries the function keys and the navigation cluster, neither of which is on the main unit at all.[1]
Deskthority gives the weights as 1005 g for the keyboard and 372 g for the keypad — 1.38 kg for the pair.[1] The FCC ID is BCGM1242 and the layouts are modified ANSI or ISO.[1]
Switches
Two mechanisms, and the difference between them is the keyboard's defining characteristic in use.
Main keys: Alps SKFS
The alphanumeric keys use Alps SKFS, from the low-profile PCB-mount SKFR/SKFS series.[1] Two things about these switches are routinely got wrong:
- They keep full 3.5 mm travel despite being low-profile — the switch body is 10.3 mm tall and includes an integrated jumper.[2] Claims of 2.5 mm or 1.5 mm travel for this keyboard are wrong.
- The keycap mount is unique to the series and is not the common Alps mount.[2] It is also not pin- or keycap-compatible with Alps SKFL. Alps-mount keycaps will not fit, and an SKFL is not a substitute.
The variant fitted here is SKFS White, Alps model SKFSAA, the tactile member of the series.[2] Its mechanism is genuinely clever: a click leaf sits in front of a chamber whose front wall is open, so when the leaf is released it has nothing to strike and makes no click sound. The result is more tactility than an ordinary tactile leaf gives, at the cost of empty space inside the switch.[2]
Deskthority's Adjustable Keyboard article describes SKFS as "clicky" on the strength of the 1994 Alps catalogue.[1] The switch article, which is based on disassembled examples and photographs of the leaf, is specific about why it cannot click.[2] The catalogue wording appears to describe the tactile event rather than an audible click; the mechanical description is the one followed here.
Function keys and navigation: microswitches
The upper navigation cluster and the function keys — all of which live on the separate keypad — are not key switches at all. They are buttons over what appear to be simple microswitches.[1] This is the keyboard's most-criticised feature: the function keys feel nothing like the main keys and take noticeably more force. No published actuation figures for them could be found and none are stated here.
ADB Behaviour
The keyboard and the keypad are two separate ADB devices. Both default to address $02, the address Apple reserves for encoded devices, which means the bus has to resolve an address collision between them at every startup: the Start Manager sends Talk Register 3 to $02, both answer, one loses the collision, and the winner is moved to a free address with a Listen Register 3 command carrying Handler ID $FE.[3]
That matters practically. If the keypad intermittently disappears, suspect collision resolution before suspecting the keypad. Apple's specification says devices should assert their start bit at a random time within the stop-to-start window precisely because two devices on nearly identical clocks may fail to detect a collision at all.[3] A marginal ADB cable or a long chain makes this worse.
Other published figures that apply:[3]
- Register 0 carries two key events in one read, so two-key reporting is normal.
- Register 2 carries modifier-key status, with 0 meaning down.
- Apple documents no polling rate; in the idle state the transceiver repeats the last Talk command every 11 ms.
- All devices on the bus together must draw no more than 500 mA, and Apple recommends no more than three devices on one ADB port. A keyboard plus a keypad plus a mouse is already at that limit.
Maintenance and Repair
Before you open it
The two units are separate assemblies with separate PCBs.[1] Diagnose which one is at fault first — they can be tested independently by plugging each in on its own.
Wrist rests keep falling off
The rests are removable by design.[1] Missing rests are the commonest thing wrong with a surviving set, and a complete set is three of them: two for the keyboard and one for the keypad.[1]
Dead or chattering main key
- Remove the keycap carefully — the SKFS mount is unique and fragile, and a broken stem cannot be replaced from any other switch family.[2]
- Flood the switch with 90%+ isopropyl alcohol, actuate repeatedly, dry fully.
- If that fails, the switch must come out. There is no drop-in substitute: SKFS is PCB-mount, has a unique keycap mount and is not compatible with SKFL.[2] A donor Adjustable Keyboard is the only realistic source. NOS SKFS switches do surface from surplus sellers.[2]
Dead function key
Those are microswitches under button caps, not key switches.[1] Clean them with contact cleaner and work them repeatedly; a generic microswitch of the same footprint is a more plausible substitute here than anywhere else on the keyboard.
Keypad not recognised
- Try the keypad alone, connected directly to the computer with nothing else on the bus. If it works alone but not with the keyboard, the problem is address-collision resolution, not the keypad.[3]
- Shorten the chain and replace suspect cables before anything else.
Split angle will not hold
The hinge is at the centre rear and the halves swing out horizontally.[1] Friction is what holds them. Do not lubricate it — that removes the only thing keeping the position.
What Is Not Documented
Apple published a great deal less about this keyboard than the collector literature implies. No dimensions, retail price, production figures, sales data, manufacturing locations, serial-number format or actuation-force figures for either mechanism could be traced to Apple or to a photograph-backed source, and none are stated here. Contemporary magazine reviews are frequently cited for this product with specific issue dates; none of those citations could be verified against the publications themselves, so no review is quoted here.
Restoration
The case and wrist rests are the parts that yellow, and the wrist rests worst of all because of skin contact. See Retrobrite before treating anything, and test on the underside of a rest first — the textured surfaces on this keyboard take treatment unevenly.
Modern Use
The keyboard and keypad are two ADB devices and therefore need either a converter with two ports or a converter plus a hub. See Apple Desktop Bus for the protocol timing any converter has to meet.
See Also
References
- ↑ 1.00 1.01 1.02 1.03 1.04 1.05 1.06 1.07 1.08 1.09 1.10 1.11 "Apple Adjustable Keyboard", Deskthority wiki. Part number M1242; FCC ID BCGM1242; modified ANSI or ISO layouts; Alps SKFS main switches with microswitches for the upper navigation cluster and function keys; PCB mount; ADB interface; weights of 1005 g for the keyboard and 372 g for the keypad; two halves hinged at the centre rear with the large space bar fixed to the centre base; removable wrist rests, one per side plus one for the keypad; and the function keys and navigation cluster being located on the keypad rather than the main unit. Photographic galleries of German QWERTZ and US/Russian JCUKEN examples, boxed contents, both PCBs and the disassembled cases. Community wiki, cited as a secondary source, photograph-backed.
- ↑ 2.0 2.1 2.2 2.3 2.4 2.5 2.6 2.7 "Alps SKFR/SKFS series", Deskthority wiki, with part numbers taken from the 1994 Alps catalogue. Low-profile PCB-mount switches that retain full 3.5 mm travel despite their size; 10.3 mm tall with an integrated jumper; the keycap mount is unique to the series and is not the common Alps mount, and the switch is neither pin- nor keycap-compatible with Alps SKFL. SKFS White (model SKFSAA) is the tactile member of the series and is the switch fitted to the Apple Adjustable Keyboard: a click leaf sits in front of a chamber whose front wall is open, so when the leaf is released it has nothing to strike and produces no click sound — greater tactility than a typical tactile leaf, at the cost of empty space inside the switch. Deskthority notes that US patent US4935591, filed 1988, resembles the design but that no patent has been confirmed for it.
- ↑ 3.0 3.1 3.2 3.3 Guide to the Macintosh Family Hardware, second edition, Apple Computer, Inc. / Addison-Wesley, 1990 — hosted on this wiki as File:Apple Guide to the Macintosh Family Hardware 2nd Edition 1990.pdf. Chapter 8, "Apple Desktop Bus": Table 8-1 connector signal assignments (470 Ω pull-up, POWER.ON on pin 2); Table 8-2 transceiver electrical characteristics; Table 8-4 register 0 in the Apple Standard Mouse and its note on 100 ±10 / 200 ±10 counts per inch; Tables 8-7 and 8-8 registers 0 and 2 in the Apple Standard Keyboard; Tables 8-10 and 8-11 registers 0 and 2 in the Apple Extended Keyboard and the $0002 → $0003 Device Handler ID change for right-hand Option and Control; Table 8-13 command byte syntax; Table 8-14 the full ADB timing specification; Table 8-15 device register 3; Table 8-16 device addresses; Table 8-17 reserved Device Handler IDs; the 500 mA total bus limit, the 5 m / 100 pF-per-metre cable limits, the 11 ms idle polling interval and the warning against unplugging a device while the computer is running. Chapter 9, "Floppy Disk Interfaces": Table 9-1 drive capacities, file systems and encoding; the IWM and SWIM interface ICs; internal 20-pin and external DB-19 pinouts; drive current requirements; and the PWM motor-speed line used only by 400K single-sided drives.