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DATAMATH CALCULATOR MUSEUM

Texas Instruments TI-55-II

Date of introduction:	1981	Display technology:	LCD
New price:	$40.00	Display size:	8 + 2
Size:	5.8" x 3.1" x 0.9"
Weight:	3.9 ounces	Serial No:	210035
Batteries:	2*LR44	Date of manufacture:	wk 37 year 1981
AC-Adapter:		Origin of manufacture:	USA
Precision:	11	Integrated circuits:	CD4555, CD4556
Memories:	1-8
Program steps:	56-0	Courtesy of:	Joerg Woerner
		Download manual:	(US-QR: 1.242 kB)

With the TI-55-II Texas Instruments added in the year 1981 a new calculator line to the existing slimline series. In you compare the slanted TI-55-II with a typical slimline calculator like the TI-53 you will notice some changes:

	Larger display gives 8+2 digits instead 5+2
	45 keys instead of 40 keys
	More space for the electronics

The display was not in one line with the keys but slanted towards the user. Together with a perfect contrast and large digits the calculator looked very professional. In practice the keyboard of all members of the slanted scientific/financial calculators was terrible, either bouncing or without any contact. Most users of the TI-55-II remember: "The -II designation was evidently for the number of keystrokes that were recorded with one button press". The calculators were usually replaced for free by Texas Instruments with TI-55-III's which did not inherit the bad genes of their forefathers.

Some very early calculators of the second generation were sold under the old designation TI-55-II. View a very rare TI-55-II manufactured in Taiwan here.

The two-chip design of most slanted calculators allowed more features compared to the slimline series. The TI-55-II for example added a total of 8 memories to the basic functions. Find more information about the TP0456 calculator chips here. The TI-88 added a third microcontroller to this Master/Slave approach.

Known from the TI-53 and the original TI-55 is the simple programmability, here each memory could be converted to 7 program steps. A nice enhancement was a function to integrate with the Simpson-rule. If you are interested in the calculating accuracy of scientific calculators, don't miss the Calculator forensics.

One calculator in the TI-55-II series - the TI-54 - could manage arithmetics with complex numbers. Once again a "first" from Texas Instruments.

Don't miss an early prototype of the TI-55-II.

In Brazil the housing of the TI-55-II was changed to accommodate two AA-sized batteries instead the small coin shaped LR44 type. View this rare beauty here.

The US based company Jeppesen Sanderson developed a very interesting navigation computer called prostar based on the TI-55-II.

If you have additions to the above article please email: joerg@datamath.org.