Texas Instruments SR-56

Introduced only few month after the SR-52 programmable, the SR-56 was it's small brother. The housing looked identical to the SR-51A, only the LRN-key gave you an idea of it's programmability. Compared to the SR-52 it uses only one instead of two memory-chips (the TMC0599), this reduced the possible programm length from 224 steps to 100 steps. Main disadvantage was the lack of a permanent storage like a card reader or the continious memory of the later TI-58C.

This calculator works with both the PC-100 and PC-100A printer craddle. 

There are two different versions of the calculator reported, one with and one without the word "Programmable" under the SR-56 logo.

The SR-56 uses like the SR-50, SR-51 and SR-52 the TMC0501 scalable calculator architecture. It is surrounded by the TMS0537 and TMC0538 SCOM (scanning read only memory) and the TMC0599 memory chip.

According to Texas Instruments the SR-56 was introduced May 21, 1976 which is around week 20 of the year. Recently french collector Francis Martin discovered two SR-56 with production codes LTA1176 and LTA1276. Dismantling the calculators gave datecodes of the two SCOM's (scanning read only memories) of week 11 in the year 1976, too. This proofs that the SR-56 were manufactured already in March and we assume that Francis is the lucky owner of rare "pre-production run" calculators.

In the meantime Ken Kaplan revealed a production code LTA0876 and datecodes on the SCOM's of week 05 in the year 1976. 

Texas Instruments introduced on May 24, 1977 the famous calculator trio TI-57, TI-58 and TI-59 replacing both the SR-52 and SR-56. German collector Stephan Feinen discovered recently a SR-56 with a production code of 2477ACH - weeks after the introduction of the successors!

Fellow collectors - if you own a SR-56 please report us the serial number and date code on the back of the calculator for our SR-56 Database.

SR-56 Database

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

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