Texas Instruments SR-52

If you call the SR-52 a pocket calculator you need really huge pockets. Introduced in Fall 1975, this wonderful calculator integrated a card reader for magnetic strips, a huge memory for 224 program steps and the revolutionary Algebraic Operating System (AOS™) into a housing similar to the SR-50A calculator. By the way, the SR-52 was the thickest calculator ever with a whooping 1.8". Together with the calculator a "Printed Cradle" PC-100 was introduced, a thermal printer and plotter which secured the SR-52. In September 1975 a the SR-52 was with a Suggested Retail Price of US$ 395 (around US$ 2,200 inflation adjusted in 2023 money) not really a bargain. The SR-52 was clearly placed against the Hewlett-Packard HP-65, later the HP-67 featured an identical memory space to the SR-52.

The SR-52 was an important milestone in the history of programmable calculators based on the TMS0500 Building Blocks for Scientific and Programmable Calculators introduced in January 1974 with the SR-50 and leading to the legendary TI-59.

The remarkable SR-52 uses most features of the TMC0500 Architecture. A deeper exploration of the calculator reveals a TMC0501 Revision E or TMC0501E Arithmetic Chip surrounded by one TMC0524 SCOM (Scanning and Read Only Memory) Chip, two TMC0561/TMC0562 BROM (Bare Read Only Memory) Chips for a combined 3k*13 Bits instruction memory.

In addition you'll notice on the printed circuit board (PCB) two TMC0599 Multi-Register Chips for program and data and finally a TMC0595 Magnetic I/O Chip controlling the internal magnet card read/writer.

A calculator with a similar feature set was sold with the huge desktop-model SR-60. The related SR-56 lacks the magnetic card reader and sports a smaller user memory.

In November 1976 Texas Instruments announced PPX-52 (Professional Program Exchange), a service for SR-52 users in the U.S., Canada and Mexico to gather, compile and redistribute programs for the calculator. It was in Fall 1977, shortly after the introduction of the TI-59, merged with the PPX-59. All PPX-52 Newsletters are available for free download as a service provided by the Datamath Calculator Museum.

Don't miss the secrets of the SR-52 and read about some Undocumented Features.

At first glance the calculating precision of the SR-52 was reduced from 13 digits to 12 digits compared with earlier scientific calculators based on the TMC0501 Arithmetic chip, for instance the SR-51. But fellow collector Palmer Hanson revealed in October 2009, almost 35 years after its introduction, the remaining secrets of the SR-52. Don't miss the Story "Twelve or Thirteen Digits on the SR-52." 

If you are interested in the calculating accuracy of scientific calculators, don't miss the Calculator forensics. 

Comparing the Constant ROM Content with the programmed constants frequently used with computing algorithm of trigonometric functions like sine, cosine, or tangent of an SR-50 manufactured in May 1974 still using the original TMC0521-2 SCOM Chip with the TMC0524B Chip of the featured SR-52 with our TMS0500 Platform after recording their ROM Images showed no differences.
If you are interested in "huge pocket calculators" you should view the Canon Palmtronic F-7 and Casio PRO fx-1.

The SR-52 is featured in the Texas Instruments Incorporated bulletins CB-SR52 dated 1975, SR-52_FL, CB-195A dated 1976 and in the Texas Instruments Deutschland GmbH leaflet ER-1976 dated 1976.

Fellow collectors - if you own a SR-52 please report us the serial number and date code on the back of the calculator for our SR-52 Database.

SR-52 Database

AOS™ is a trademark of Texas Instruments.

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

© Joerg Woerner, December 5, 2001. No reprints without written permission.