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TI-30XA (2013): retained the size and shape of the 1996 model, having buttons rounded on the bottom, and the color of the "2nd" button changed from yellow to green. With introduction of a new circuit board in 2015 the logarithm bug was fixed, [ 4 ] also the calculator switched to using just one 1.5V battery instead of two.
HP-19C calculator HP-29C with AC-powered battery charger. The HP-19C and HP-29C were scientific/engineering pocket calculators made by Hewlett-Packard between 1977 and 1979. They were the most advanced and last models of the "20" family (compare HP-25) and included Continuous Memory (battery-backed CMOS memory) as a standard feature.
Replacement battery packs are no longer available, leaving existing HP-35 calculators to rely on AC power, or their users to rebuild the battery packs themselves using available cells. An external battery charger was available, and the calculator could also run from the charger, with or without batteries installed.
The calculator was code-named Wizard, [4] which is the first known use of a code name for a calculator. It also contained an Easter egg that allowed users to access a not-especially accurate stopwatch mode. [5] [6] An accurate version of the stopwatch mode was officially featured in the 1975 successor of the HP-45, the HP-55.
Button, coin, or watch cells. A button cell, watch battery, or coin battery is a small battery made of a single electrochemical cell and shaped as a squat cylinder typically 5 to 25 mm (0.197 to 0.984 in) in diameter and 1 to 6 mm (0.039 to 0.236 in) high – resembling a button.
SR-50 (1974) Printed circuit board. Data code 035: 3rd week 1975. The SR-50 was Texas Instruments' first scientific pocket calculator with trigonometric and logarithm functions. . It enhanced their earlier SR-10 and SR-11 calculators, introduced in 1973, which had featured scientific notation, squares, square root, and reciprocals, but had no trig or log functions, and lacked other featur
Cost and thermal issues limit how much power the rectifier can handle, so beyond approximately 240 V AC and 75 A it is better for an external charging station to deliver DC directly to the battery. For faster charging, dedicated DC chargers can be built in permanent locations and provided with high-current connections to the grid.
Perhaps the HP-42S was to be released as a replacement for the aging HP-41 series as it is designed to be compatible with all programs written for the HP-41. Since it lacked expandability, and lacked any real I/O ability, both key features of the HP-41 series, it was marketed as an HP-15C replacement.