• Country
• United States of America (USA)

• Manufacturer / Brand
• Hewlett-Packard, (HP); Palo Alto, CA

• Year
• 1975–1978

• Category
• Signal Processing and Computing

• Radiomuseum.org ID
• 305084

Click on the schematic thumbnail to request the schematic as a free document.

• Wave bands
• - without

• Power type and voltage
• Storage Battery for all (e.g. for car radios and amateur radios) / NiCd: 2 x 1.2 Volt

• Loudspeaker
• - - No sound reproduction output.

• Material
• Plastics (no bakelite or catalin)

• from Radiomuseum.org
• Model: Electronic Pocket Calculator HP-21 - Hewlett-Packard, HP; Palo Alto

• Shape
• Very small Portable or Pocket-Set (Handheld) < 8 inch.

• Dimensions (WHD)
• 68 x 28 x 130 mm / 2.7 x 1.1 x 5.1 inch

• Notes

• Introduced in 1975, the HP-21 (codenamed Pumpkin) is a basic 30-key scientific calculator that replaced the HP-35. It has the same functions as the HP-35 plus controlled display formatting, polar/rectangular conversion, radian mode in trigonometric calculations, and storage arithmetic.

  RPN logic, 4 level stack.
  10-digit precision.
  11-digit plus sign LED display. The decimal point is integrated in the digits instead of taking up one digit position, as in the HP-35. The exponent sign and digit share space with the mantissa when required.
  Fixed and scientific number format, selectable by the DSP key.
  Storage arithmetic with dedicated keys (using shift).
  Slide switch selection of degrees or radian mode.

  Power 2.5v 500 mW.
  An internal 2-transistor blocking oscillator converter generates +6v and -12v for the MOS ICs and +4v for the LED display.

  Battery pack HP82019A/B contains 2 AA-size rechargeable NiCd batteries. The B model can hold batteries of slightly larger diameter than the A model.
  Spurious decimal points are displayed when the battery is low.

  Charger HP82024A.
  Input switch selectable 115v/230v AC.
  Output 10v AC 180 mA.
  (The charger only contains a transformer).

  The calculator can be operated from the charger, but as the batteries are necessary to clamp the supply voltage they must be present to avoid overvoltage.

  An HP82028A reserve power pack contains the rectifier diode and series resistor that allows an HP82019A/B battery pack to be charged outside the calculator using the HP82024A charger.

  Calculator and charger made in Singapore.

• Net weight (2.2 lb = 1 kg)
• 0.170 kg / 0 lb 6 oz (0.374 lb)

• Price in first year of sale
• 125.00 USD

• Author
• Model page created by Bruce Taylor. See "Data change" for further contributors.

• Other Models

• Here you find 393 models, 361 with images and 138 with schematics for wireless sets etc. In French: TSF for Télégraphie sans fil.
  All listed radios etc. from Hewlett-Packard, (HP); Palo Alto, CA