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Touch Activated Switch Arrays, Inc., typically written as TASA Inc, was an American manufacturer of flat panel keyboards and other input devices. TASA claim to have been formed in 1975, and this matches the Delaware business records that shows a Touch Activated Switch Arrays, Inc. incorporated there on the 22nd of May 1975. California business records show a Touch Activated Switch Arrays, Inc. from Delaware that was registered on the 21st of April 1976, which may be the date that the business was registered for trading in Califoria; it appears that the company relocated from Delaware to Santa Clara, California. Separately, a business named TASA, Inc. (the name that TASA typically used) was registered in California on the 23rd of February 1978; any relationship between this TASA and Touch Activated Switch Arrays is unknown; the address for the foreign business from Delaware is the one that matches the published address for TASA in 1978 and 1981, and the full name was still in use in 1981.



In the late 1970s, TASA introduced flat panel keyboards with no moving parts. Although visually similar to RCA’s VP-600 series of flat keyboards, RCA used membrane switches while TASA’s approach is capacitive. According to the patent, TASA keyboards are capacitively encoded: each switch uses no fewer than seven capacitors. The operator’s finger forms half of a capacitor that effectively grounds that key to AC. The internal side of each key’s capacitor is in turn connected to another six capacitors, one per output bit, each one being wired to either the one (1) line or the zero (0) line for that bit. Only the one line is fed into the output stage, but the zero line is nonetheless used in the key detection process. Each output bit is considered valid so long as either a zero or one is asserted: the zero and one lines are fed into an exclusive-OR (XOR) gate, whose output is true so long as either a zero or one has been asserted. A valid keypress is only recognised so long as every output bit is being asserted (all XOR gates are true, their outputs in turn being fed to an AND gate).

The use of zero lines provides validity checking: if both the one and zero line is active simultaneously, then the input into the keyboard is invalid. It also allows the full 64 keys to register, as otherwise a key without output code of zero would not register.

The patent only provides for six output bits per key, for a total of 64 possible keys. As such, each key is numbered from 0 to 64. Some other means is required to translate the key positions to output codes. A separate encoder circuit—CMOS/LSI ICs are said to be used—would have included the relevant look-up table as well as Control and Shift key handling and the electronic hysteresis advertised.

The idea of typing on a perfectly flat, unyielding surface never gained ground: forty years on, desktop and notebook computers alike still universally provide keyboards with moving keys, although the travel and tactile feedback in some notebook keyboards is so reduced as to be barely different from TASA’s invention. However, the introduction of Apple’s iPhone reintroduced the idea of typing on a flat surface, which is now the standard input method of mobile phones and—unless an external keyboard is attached—tablets also.


TASA referred to their keyboards as “Micro Proximity”, and produced both enclosed and unenclosed keyboard units.

In a price list of unknown date, as Model 55 keyboard cost $80, while the Model 16 keyboards cost $60 each. However, a 1978 advertisement in BYTE magazine for the Micro Proximity Keyboard (appears to be a Model 55) was stated to cost $49.95. (The advertisement in BYTE gives the count of keys as 51, but there are 55 keys; they appear to be discounting the modifier keys from the total count.)


Around the start of the 1980s, TASA introduced an “X-Y controller”, the Model 4460 X-Y Positioner, as seen advertised briefly in InfoWorld on the 1st of September 1980. This four-inch-square device, using TASA’s Touch Graphics™ technology, is a very early touchpad. The electronics involved were presumably much more complicated than those in the keyboards or the Ferenstat, as the OEM quantity price in September 1980 was $500.


Patent Title Filed Published Product
US 4221975 Touch activated controller and method 1978-04-19 1980-09-09 Ferenstat™ solid-state fader
US 4321479 Touch activated controller and method 1978-04-19 1982-03-23 Ferenstat™ solid-state fader
US 4288786 Touch sensing keyboard construction 1979-01-15 1981-09-08 Keyboards
US 4455452 Touch activated controller for generating X-Y output information 1982-09-13 1984-06-19 Touchpad


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See also