LED Displays - Electronic Calculators and Clocks

Texas Instruments did not only invent the Integrated Circuit (IC) but demonstrated in 1967 with the Cal-Tech project that a portable electronic calculator can be designed using only 3 LSI circuits (Large Scale Integration) with a complexity of about 1,000 transistors, each and some additional shift registers for data storage. While rather large high-voltage Nixie tubes worked well with electronic desktop calculators, decided Texas Instruments to develop a compact, solid state thermal printer for the Cal-Tech feasibility study and when Canon introduced in April 1970 with the Pocketronic the first portable calculator based on Texas Instruments' LSI chips, it made consequently use of a serial thermal printer. Sanyo followed soon with the slightly larger ICC-82D using Nixie tubes while Sharp introduced in November 1970 the EL-8, an even smaller portable calculator using a VFD (Vacuum-Fluorescent-Display). Meanwhile Monsanto had developed with the MAN1 the first commercial available Seven-Segment LED Display with 0.27" (7 mm) character height using 14 individual GaAsP (Gallium Arsenide Phosphide) chips for the segments and 1 LED chip for the decimal point. Monsanto followed soon with the miniaturized MAN3 display with 0.115" (3 mm) character height that could be operated at currents as low as 1 mA per segment and was hence a perfect choice for electronic pocket calculators like the Bowmar 901B. When Texas Instruments announced on September 17, 1971 with the TMS1802NC the first available standard calculator building block on a chip, it was supported by two pre-configured Multi-Digit Calculator Numeric Seven-Segment LED Displays (DIS40, DIS95) based on the TIL360 arrays, the corresponding segment drivers (SN75491) and digit drivers (SN75492) and even the 1KS/6KS Klixon™ keyboard.

When Texas Instruments announced in April 1972 the TI-2500 Datamath portable calculator and the desktop models TI-3000 and TI-3500, the calculators used different display technologies. While the TI-2500 was using the red DIS40/DIS95 LED Displays, relied the two desktop models on orange gas-discharge displays with either 8 or 10-digits marketed by Burroughs as Panaplex™ display. Main disadvantage of these technologies was their high power consumption, later calculators switched VFD technology before finally replaced by LCDs (Liquid-Crystal-Displays).

With LED Displays being one of the main cost drivers in early portable electronic calculators, their manufacturing technology was changed multiple times over a rather short time span between 1971 and 1975 before more or less extinguished before the end of the Seventies.

Single-Digit Module LED Displays

Monsanto pioneered Seven-Segment LED Display based on individual GaAsP (Gallium Arsenide Phosphide) chips and introduced in 1971 with the MAN3 (clear epoxy, flat package) a very compact design with a housing of just 0.185" (4.7 mm) width, allowing very compact Multi Digit Display Modules having a character spacing of about 0.2" (5.1 mm). The more common MAN3A changed the color of the housing to a dark red epoxy, and introduced an inline package for through-hole mounting in addition to the flat package suitable for surface mounting. Both the dimensions and pin-out of the MAN3A evolved into a de facto standard and TI's DIS279 kept its dimensions while adding a small magnifying lens that the later DISXXX dropped. 

Type Year Number of Digits Calculator Comments
MAN3A 1971  1  Bowmar 901B  
DIS279 1973  1  SR-10 Version 2, SR-50, SR-51  
DISXXX 1973  1  SR-11 Version 1  

Multi-Digit Module LED Displays

First Multi-Digit Calculator Numeric Seven-Segment LED Displays with Right-Hand Decimals introduced together with the TMS1802NC single-chip calculator circuit. The Digit and Decimal GaAsP (Gallium Arsenide Phosphide) LED chips are mounted on a ceramic header which is then hermetically sealed with a glass cover. Character-to-character spacing is maintained when multiple displays are mounted end-to-end. 

Type Year Layout and # of Digits Calculators Comments
TIL360 1971  6   Canon LE-10, SR-10  
DIS40 1971  5 TI-2500  
DIS95 1971  4 TI-2500  

Calculator Displays using Multi-Digit LED Modules


Calculator Displays using Single-Digit LED Modules


Calculator Displays using LED Chips and Protection Lens


Calculator Displays using LED Chips and Magnifying Lens


Clock Displays using LED Chips, Reflector, and Protection Lens


Type Year Layout and # of Digits Clocks Comments
TIL370 1974  4   TI-70, TI-71  

Multi Digit Stick LED Display 


Type Year Number of Digits Calculator Comments
TIL233 1975  9  TI-1200   
TIL393-6    6    
TIL393-8    8    
TIL393-9    9    

Panaplex™ and Planar-Gas-Discharge Display


Type Year Number of Digits Calculator Comments
SP-352 1972  2    
SP-353 1972  3 Heathkit IC-2008A  

VFD (Vacuum-Fluorescent-Display)


Type Year Number of Digits Calculator Comments
Itron FG85CI    9 TI-1025, TI-1050  

LCD (Liquid-Crystal-Display)


Type Year Number of Digits Calculator Comments


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