Additional Pictures 


The TP0456 microcomputer based Primary-Secondary architecture found in the TI-55-II calculator.
The CD4556 is the Primary chip, the smaller CD4555 the Secondary chip.

From left to the right three different TI-55-II and TI-55-III printed circuit boards (PCBs):
(1) TI-55-II manufactured in the year 1981 in US. Famous for the bouncing keyboard introduced with the
slimline calculators.
(2) TI-55-II resp. TI-55-III manufactured in the year 1985 in Taiwan. Uses two PCBs, one for the keyboard,
one for the main electronics.
(3) TI-55-III manufactured in the year 1986 either in US or Italy. Uses Far-East keyboard technology with conductive
rubber together with contact fingers on a flexible PCB.

horizontal rule

If you have additions to the above article please email:

Joerg Woerner, October 11, 2002. No reprints without written permission.