Tactile (pronounced tak-til or tak-tahyl)
(1) Of, pertaining to, endowed with, or affecting the
sense of touch.
(2) Perceptible to the touch; tangible.
(3) Capable of being touched; tangible (archaic).
1605–1615: From the Middle French tactile, from the Latin tāctilis
(tangible), from tāctus, past participle
of tangere (to touch)), from the
primitive Indo-European root tag (to touch; to handle). The construct was tact(us) + ile. The –ile suffix was from the Latin –īlis (neuter -ile, comparative -ilior,
superlative -illimus or -ilissimus; the third-declension
two-termination suffix), from the Proto-Italic -elis, from the primitive Indo-European -elis, from -lós. It was used to form an adjective noun of
relation, frequently passive, to the verb or root. The meaning "of or pertaining to the
sense of touch" is attested from the 1650s. Tactile is an adjective, tactilize is a verb, tactility is a noun and tactilely is an adverb; the noun plural is tactilities.
Audiotactile: (relating to the senses of hearing and touch).
Chemotactile: (the ability of an organism to sense changes to its chemical environment).
Electrotactile: (composed of an array of small electrodes that provide stimulation to the skin).
Entactogen: (the quality of combining mechanosensory (of or pertaining to the sensing of mechanical stimuli) with tactility).
Mechanotactile: (mechanosensory (of or pertaining to the sensing of mechanical stimuli) and tactile).
Orotactile: (of or pertaining to the sense of touch in mouth).
Pedotactile: (that can be felt by the feet).
Pneumotactile: (relating to the skin's ability to feel a pneumatic pulse).
Protactile: (a dialect of ALS (American Sign Language) that communicates with touch).
Tactilometry: (The measurement of touch or of vibration (change in dimension) (tactilometric the adjective).
Teletactile: (relating to the transmission of physical touch over a telecommunication network (teletactility the noun).
Thermotactile: (Sensitive to heat and to touch (but distinct from thermomreactive)).
Visuotactile: (relating to perception by vision and touch).
Vibrotactile: (of, pertaining to, or using vibrotaction (the dynamic response of tactile nerve endings in the skin to vibration)).
Tactile Paving
Examples of tactile pavers.
Tactile graphics (the singular form does exist but is rare and restricted to technical use (software manuals and such)) are raised-surface representations of images, maps, graphs and diagrams designed for individuals who are blind or visually impaired, enabling them to explore (using touch) anything able to be represented thus (physical topography, complex STEM (science, technology, engineering, math) content (cabling diagrams the classic example) spatial layouts, art etc). Tactile paving was a practical application of tactile graphics, describing a system of textured ground surface indicators (constructed typically using a brightly colored rubberized plastic) permanently affixed to stairs, railway station platforms, the point at which a sidewalk (footpath) ends (the so-called “curb-cut”) and access to a pedestrian road-crossing begins etc. The concept first appeared in Japan in the mid-1960s and was based on 点字ブロック (tenji (the name for Japanese braille, a system of writing in which letters and some combinations of letters are represented by raised dots arranged in three or four rows of two dots each and are read by the blind and partially sighted using the fingertips; the system was named after French educator Louis Braille (1809–1852))). Something like “braille writ large” the “tactile paving tiles” are there as a kind of “signage” for the blind or visually-impaired, designed specifically easily to be detectable by shod-feet or a hand-held cane; the system was a major contribution to making the built environment more easily negotiable. Although the shapes (“blister”, “lozenge”, “ribbed”, “cycleway”, “directional”, “stair” etc) are not quite internationally standardized, within jurisdictions, there is one for railway platforms, one for stairs, one for curb-cuts etc, the latter of importance because there’s sometimes no grade-change between a sidewalk and roadway along which motorized vehicles pass.
Tactile Necrophilia
In psychiatry, “tactile necrophilia” (a condition in which subjects sexually are aroused by touching or stroking a corpse, without engaging in intercourse) is one of the ten classifications of necrophilia defined by Indian forensic psychologist Professor Anil Aggrawal (b 1956), author of the 438 page Forensic and Medico-legal Aspects of Sexual Crimes and Unusual Sexual Practices (2008), described in a review published in the AAJFC (American Academy Journal of Forensic Sciences) as a “quite remarkable book” and an “authoritative text” in which “Dr Aggrawal deftly brings to bear his 25 years of interest and knowledge of sexual deviancy”. Within the profession, Dr Aggrawal is considered the leading authority on necrophilia and, as well as being a text book for the profession, Forensic and Medico-legal Aspects of Sexual Crimes and Unusual Sexual Practices is also a valuable contribution to the evolution of the history of how “normal” & “abnormal” have at various times been constructed, one reviewer noting “a enjoyable aspect of this book is Dr Aggrawal’s grasp of ancient references concerning the paraphilias in both religious and historical texts” while another was pleased by the inclusion of “minor aberrant behavior such as coprolalia and troilism.”
The ten classifications are not listed in either the APA’s (American Psychiatric Association) DSM (Diagnostic and Statistical Manual of Mental Disorders) nor the WHO’s (World Health Organization) ICD (International Classification of Diseases), and in the latest edition of the DSM (DSM-5-TR, 2022), a recurrent, intense sexual interest in corpses is classified as diagnosable under “Other Specified Paraphilic Disorder (necrophilia)” when “the cause of marked distress or impairment in important areas of functioning.” Intriguingly, Professor Aggrawal list his ten headings in order of “increasing severity” meaning an “Exclusive Necrophiliac” (Class X; Those for whom sex with a corpse is an exclusive interest (ie they do not respond to a living partner)) is defined as a more severe condition than that of the “Homicidal Necrophiliac” (Class IX; Necrosadists, those who commit murder in order to have sex with the victim). Presumably the notion of “severity” explored by Professor Aggrawal is based on a scale where the “total exclusion” of sex with a living human is the “terminal state” and one can see his point but it’s suspected most non-clinicians would regard (certainly on public policy grounds) someone who murders their sexual partners to be a “more severe” state of mental disorder than one who enjoys partners who met their end by other means (acts of God, trauma, murdered by the Freemasons, fatal illness etc). Still, Professor Aggrawal is thought the world’s “leading authority on necrophilia” so we should defer to his expertise; it should be added his ten categories are to be digested while remembering he is a practicing forensic psychologist, his findings empirical and not theoretical:
Class I: Role players (Those aroused when pretending
their partner is dead during sexual activity).
Class II: Romantic necrophiliacs (The bereaved people who remain
attached to their dead lover's body).
Class III: Necrophiliac fantasizers (Those who fantasize about
necrophilia, but do not physically interact with corpses).
Class IV: Tactile necrophiliacs (Those aroused by touching or
stroking a corpse, without engaging in intercourse.
Class V: Fetishistic necrophiliacs (Those who remove objects or body parts
from a corpse for sexual fetishes, without engaging in intercourse).
Class VI: Necromutilomaniacs (Those who derive pleasure from
mutilating a corpse while masturbating, without engaging in intercourse).
Class VII: Opportunistic
necrophiliacs
(Those who usually have no interest in necrophilia but avail themselves of the opportunity
when presented).
Class VIII: Regular necrophiliacs (Those who preferentially (but not
exclusively) have intercourse with the dead).
Class IX: Homicidal necrophiliacs (Necrosadists; those who murder
someone to have sex with the victim).
Class X: Exclusive necrophiliacs (Those for whom sex with a corpse
is an exclusive interest (ie they do not respond to a living partner)).
Tactility's finest hour: The IBM Model M keyboard.
In the few decades computing has been a mainstream activity, in the layers, at various points, such as been the variety of hardware, operating systems, languages and software, often there's been no general agreement about what’s best in any particular field but most with any exposure to the IBM Model M keyboard agree it’s probably the finest keyboard ever. Even those not attracted to the tactility that is its most obvious characteristic (and there are those gentle souls who prefer a “squishy” to a “clicky” keyboard) will usually concede the build quality is exceptional, compared especially to some of the flimsy devices in recent years bundled with systems. It shouldn’t be surprising IBM was able at scale to build something like the Model M keyboard given the company’s decades of experience in engineering such constructions and there are Model M nerds prepared to believe all those years were but preparation for what was required to make the Model M a landmark in tactility.
IBM (International Business Machines) began in New York in 1888 (adopting the initialism in 1924), its early core-business mechanical “tabulating systems” for accounting and time-keeping and, by the 1930s, some of the mechanical engineering used in these systems was applied to typewriter technology after it acquired the tools, patents and production facilities of Electromatic Typewriters of Rochester. The first result of an intense R&D (research & development) effort was released in 1935 as the Model 01 IBM Electric Typewriter, the machine that became the first really successful electric typewriter in the US and the beginning of a line which, by 1961, had evolved into the IBM Selectric, famous for its “element” that the rest of the world came to call the “golfball”. The almost spherical “golfball” (it appears also in some IBM documents as “typeball”) contained the impressions of the letters that struck the ribbon and was interchangeable with others using different font sets. That was not a new idea, other manufacturers using the principle of interchangeability in the late nineteenth century but with “type wheels” that were larger and tended to be fragile; the three-dimensional “golfball” was both more robust and, having to travel a smaller distance per key stroke, permitting a faster typing rate. It was with the Selectric the evolution of what became the Model M keyboard really began.
Though the unit on the 1935 Model 01 Typewriter may be thought the Model M's LCA (last common ancestor), it's the Model F that deserves the honor of parenthood. The first version of the definitively tactile, stand-alone IBM keyboard was the Model 14 which, although most associated with the original IBM PC-1 released in August 1981, had actually debuted with the System/23 Datamaster (1981-1985), a short-lived corporate workstation that proved a dinosaur, unable to adapt to the strange new world created by the unexpected success of the PC-1 (those in the IBM boardroom as surprised as any). The adoption by corporations and SMBs (small & medium business) of the PC-1 and its successors was also ultimately the death knell for the earlier 6580 Displaywriter (1980-1986), a hefty and expensive dedicated word-processor (the impact printer usually bundled with the thing so loud most put it in an insulated shroud or a separate room); like the System/23 in the battle of "survival of the fittest", it proved unable to adapt, crowded out of the ecosystem by the rapidly expanding niche created by the PC-1. In an era when "to be first" was often a great marketplace advantage (enabling critical mass to be gained), the Datamaster's introduction five weeks ahead of the PC-1 wasn't enough for the species to survive although it's Model 14 keyboard was shared with the upstart from which not much had been expected. The Model 14 debuted with an 83 key layout and the nerdiest of nerds still extol its technical superiority over the Model M in that it uses a buckling spring over a capacitive PCB (printed circuit board) rather than the later membrane. The Model F remained in production until 1985 (although volumes (by both IBM and Lexmark) had slowed) but it was the platform for innovations such as the revised layout to accommodate the PC-AT's protocols and the availability of specialized models with provision for magnetic stripe readers & inbuilt LCD readouts (both with cable-interfaces to external devices) and as few as 50 or as many as 127 keys (the latter industry-specific).
Model F aficionados can be a snobby crowd, proud of pointing out even IBM admitted one of the design objectives with the Model M was to reduce manufacturing costs but the attraction is real, the intricacies of the Model F intriguing and their labour-intensive production process does mean nothing like them is likely again to be made. The internal assembly uses two curved metal back-plates and the PCB is flexible, thus also curved when attached to the back-plate and while just about every other keyboard's curves are simulated by the molding of the keycap profiles, the Model F's curves were integral to the frame, thus allowing all keycaps to be the same shape and size, a great advantage for those who like to tinker and customize. While freaks customizing keyboards are less frequently found than once they were, they exist still in dark rooms living on pizza and Coca-Cola. Snobbery or not, the freaks do (up to a point) have a point because the mechanical advantages are real. The capacitive design is superior, requiring a lighter actuation force, delivering a crisper feel and slightly sharper feedback; it’s also more robust, IBM guaranteeing each key with a MTBF (mean time between failure) of over 100 million key-presses, a reasonable life even for the most productive trolls. The switch from PCBs to membranes meant these characteristics were to some degree toned down in order to lower manufacturing costs although the MTBF was still rated an impressive 80 million, even a Marcel Proust (1871-1922) unlikely to have worn one out in his lifetime.
Pace the freaks but the Model M is preferable, if for no other reason than simply because it (more-or-less) standardized the core keyboard layout (most others have long conformed) and in use, the tactility is little different from its predecessor. Regarding the layout, the case can be made that the Model F’s location of the function keys to the left may have made sense but the planet has settled on the Model M's layout and humans adapted. Introduced in 1985 with the 3161 terminal, the PC-compatible version appeared in 1987 when it was included with the PS/2 range introduced with the OS/2 operating system and MCA (Micro Channel Architecture) bus. The Model M is a solid (9 lb (4 kg)) tactile experience that feels as solid (and "clicky") as the Model F and users typically have a long time to become accustomed to that feel; the keyboards, some now over 40 years old, appearing not to have a life expectancy, many in continuous use for decades and a servicing ecosystem exists should any parts need to be replaced although it’s said rectifying the consequences of spills (of coffee, red wine, G&Ts etc) is a more common request and, as a general principle, the higher a liquid's sugar content, the more difficult the task. Black tea or coffee with no sugar is, for many reasons, recommended, keyboard hygiene included. The best source for the tactile status symbols is ClickyKeyboards.
It will be appreciated with regard to the
figures that depression of the key button 1 moves the key button and its stem 6
into the housing 3, creating longitudinal compression and lateral deflection of
the helical compression spring 2. An initial counter-clockwise moment is
exerted on the rocker member 4 which is approximately equal to the force F
times the distance between the pivot point 8 of the rocking member 4 and the
center line of the spring. The upper end of the helical spring 2 is held
squarely against the key button 1 by a clockwise moment created by a force
equal to approximately F times the diameter of the spring divided by two. The
rocker member 4 will initially be held firmly over the contacts 5A and 5B. As
the lateral motion of the center of the helical compression spring 2 increases,
both the top and bottom reaction moments in spring 2 are decreased because F is
transmitted through the center section of spring 2. Shortly after these moments
approach 0, the rocker member rocks to a position squarely over contacts 5A and
5C and the top of spring 2 rocks about the right hand edge of its topmost coil.
The constraints upon the depression column spring have changed from an initial
end clamped condition to an end clamped-pinned condition. This sudden change
provides the tactile response of the key and is accompanied by a sudden rocking
action of the rocker member 4 which creates an acoustic feedback as well.
Evolution of the IBM Keyboard layout: Model M, 3161 Terminal (1985) & PS/2 (1987) (top), Model F, PC-AT (1984) (centre) and Model F, PC & XT, (1981) (bottom).
The "buckling spring torsional snap actuator" is the core of the Model M’s charm. Unlike mechanical switches that are depressed straight down like plungers, the Model M has springs under each key that contract, snap flat, or "buckle," and then spring back into place when released. This provides the audible “click” so associated with the model and which some don’t like but for those who become accustomed to typing on one, it’s hard to go back to anything else; they have the feel of a pre-modern (circa 1980 and earlier) Mercedes-Benz. Because of the physicality, typing on a Model M is a tangible experience; like a typewriter, the tactility and the feedback of the click gives every letter a physical presence.
NASA's (National Aeronautics and Space Administration) LSLF (Lunar Sample Laboratory Facility).
The LSLF is NASA's repository and laboratory facility at the Lyndon B. Johnson Space Center in Houston (named after Lyndon Johnson (LBJ, 1908–1973; VPOTUS 1961-1963 and POTUS 1963-1969 who, as VPOTUS was made titular head of the US space programme, the centrepiece of which was the Apollo project that produced the manned landing on the Moon in July 1969). Since 1979, the LSLF has housed geologic samples collected from the lunar surface during the Apollo missions (1969-1972). The facility preserves in a secure vault much of the 842 lb (382 kg) of rocks, dust and such returned to Earth as well as some other material and the associated data records. The facility also contains "clean-room" laboratories so samples can be processed and studied in a contamination-free environment.
A "NASA office", circa 1989 (given the likely spec of the PC, probably a secretary's desk, left) and the "moon rocks" available for "public touch".
The LSLF also includes (as a "static exhibit", left), a replica of a room in the Space Center as it was in the late 1980s. On the desk is Model M keyboard connected to a IBM PS/2 PC that, on the basis of the cropped image, appears to be a Model 30, a "low end" version that would have included either an 8086 (8/16 bit) or 20286 (16/16 bit) Intel CPU (central processing unit) and in either case would have been built on the AT (Advanced Technology) bus, later known as ISA (Industry Standard Architecture). Higher end models included the 80386 (32/32 bit) CPU and MCA, some even with the new OS/2 operating system. For a number of reasons (technological and economic), MCA and OS/2 proved to be chimeras although OS/2 did become a fabulous beast, lasting in its niche into the twenty-first century and hobbyists still support development on the platform. The LSLF's PS/2 may be running IBM PC-DOS 4.01, a "bug-fix" of the prematurely-released v4.0 that shipped with "bugs" in the handling of the then novel EMS (Expanded Memory Specification) on non-IBM expansion boards; memory was in the 1980s of great interest as users needed ways to "work-around" DOS's by the infamous 640 kb "addressable limit". Microsoft "bug-fixed" v4.0 and this was released by IBM as PC-DOS 4.01; while MS-DOS 4.0 was always the "debugged" version, very few copies were shipped so numbered, a "cosmetic release" as 4.01 soon in the channel because of the reputation of v4.0 as "flawed". Despite that, there's nothing to suggest pristine copies (ie still in shrink-wrap) of MS-DOS 4.0 have become even a minor collector's item. Also in the LSLF is a display of (right) the world's only eight lunar rocks (some nearly four billion years old) available to be touched by the general public.



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