Sharp Compet 30/Model CS-30A and Model CS-30B
CS-30A Image Courtesy of Mr. Takaharu Yoshida

There were two versions of the Compet 30 developed and marketed, the CS-30A, and the CS-30B. While visually very similar, the two versions of the machine were quite different. The CS-30A was announced in the latter part of 1966, with the CS-30B superceding the CS-30A in the spring of 1967.

The reason that the CS-30B was developed to replace the CS-30A is that the CS-30A did not not have the ability to represent negative numbers. For example, if one carried out a calculation that would normally result in an answer of -2, the calculator would display 99999999999998, e.g., the tens complement of the answer. This shortcoming was corrected in the CS-30B, by inclusion of the ability to display negative numbers correctly. An incandescent indicator behind a red filter in the shape of a minus sign, located at the right-most end of the display panel, would light to indiate a negative number. Another improvement incorporated into the CS-30B was the addition of two indciators located at the left end of the display. The top indicator would light a red "E" if an error condition occurred. Below the error indicat was another indicator that would light up as a yellow "M" to show that the memory register contained non-zero content. The CS-30A had no such indication, meaning the user would have to remember if there was any content in the memory register.

Both the CS-30A and CS-30B used static Nixie drive circuitry (not multiplexed), identical keyboard and Nixie display assemblies, and appear to be visually identical other than the added indicators at the left end of the display on the CS-30B. The general architecture of the CS-30A/CS-30B is similar to that of earlier, but lesser-featured Sharp Compet 15 calculator.

The Old Calculator Museum is interested in acquiring either version of the Compet 30 in any condition.