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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.
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.
HP-19B, introduced on 4 January 1988, along with the HP-17B, HP-27S and the HP-28S, and replaced by the HP-19BII (F1639A) in January 1990, [2] was a simplified Hewlett Packard business model calculator, like the 17B.
The calculator uses the proprietary HP Nut processor produced in a bulk CMOS process and featured continuous memory, whereby the contents of memory are preserved while the calculator is turned off. [13] Though commonplace now, this was still notable in the early 1980s, and is the origin of the "C" in the model name.
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.
A partially disassembled Curta calculator, showing the digit slides and the stepped drum behind them Curta Type I calculator, top view Curta Type I calculator, bottom view. The Curta is a hand-held mechanical calculator designed by Curt Herzstark. [1] It is known for its extremely compact design: a small cylinder that fits in the palm of the hand.
HP-65 in original hard case with manuals, software "Standard Pac" of magnetic cards, soft leather case, and charger The HP-65 is the first magnetic card-programmable handheld calculator. Introduced by Hewlett-Packard in 1974 at an MSRP of $795 [ 1 ] (equivalent to $5,069 in 2024) [ 2 ] , it featured nine storage registers and room for 100 ...
Mercury battery "РЦ-53М"(RTs-53M), Russian manufactured in 1989. A mercury battery (also called mercuric oxide battery, mercury cell, button cell, or Ruben-Mallory [1]) is a non-rechargeable electrochemical battery, a primary cell. Mercury batteries use a reaction between mercuric oxide and zinc electrodes in an alkaline electrolyte.