You can freely build on How Texas Instruments Invented the Handheld Electronic Calculator

What this patent covers

The patent details a system that shrinks bulky desktop calculator components into a handheld device. It uses an integrated semiconductor circuit array—a single chip—to handle memory storage, arithmetic operations like addition and division, and control signaling. The design stacks the keyboard, the circuit array, and the display in parallel planes to minimize the device's footprint. This allows the calculator to process multi-digit numbers and display results on a small screen or via a thermal printer while running on battery power.

What is now free to use

All 1 claims of US 3819921 are in the public domain. Specifically:

The 1 dependent claim add narrowing limitations and are also free.

What is NOT covered

Patent expiry frees this specific invention. Separately-patented improvements made after expiry may still be protected.

• Does not cover non-electronic or mechanical calculators (e.g., slide rules or abacuses).

• Does not cover calculators that require external power sources or wall outlets.

• Does not cover computing devices that lack a physical keyboard input mechanism.

• Does not cover general-purpose computers or microprocessors not specifically configured for arithmetic calculation.

Who is building on this today

Texas Instruments remains a major player in semiconductor design and embedded processing. The architecture established here is the direct ancestor of the system-on-a-chip designs used by companies like Apple, Qualcomm, and Samsung to power modern mobile devices.

Products built on expired version of this technology

How to cite this patent in your documentation

Texas Instruments Inc. US Patent 3819921. Miniature electronic calculator. Granted 1974, expired 1992. Now in the public domain.

Note: This is a convenience citation. Consult a patent attorney for formal freedom-to-operate analysis.

PatentBrief is an educational resource and does not provide legal advice. Patent expiration information is derived from USPTO records and may not reflect continuation patents, divisional filings, or separately-patented improvements. For commercial use or production decisions, obtain a formal freedom-to-operate (FTO) opinion from a registered patent attorney.