You can freely build on Hedy Lamarr and George Antheil's Frequency Hopping Secret Communication System
This patent expired in 1961. Every claim — 0 independent, 0 dependent — is now unenforceable. Anyone can use, reproduce, manufacture, sell, or offer for sale this technology without a license.
Original assignee
Individual
Patent granted
1942
Expired
1961
Forward citations
82
What this patent covers
The system uses two synchronized mechanisms, similar to those found in player pianos, to change the carrier frequency of a radio transmitter and receiver simultaneously. By rapidly switching frequencies in a predetermined sequence, the signal becomes extremely difficult for an adversary to detect or jam. The patent describes using perforated paper rolls to control the timing of these frequency shifts, ensuring both the sender and receiver stay perfectly aligned.
What is now free to use
All 0 claims of US 2292387 are in the public domain. Specifically:
The 0 dependent claims 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 digital frequency hopping methods using modern microprocessors.
Does not cover encryption or scrambling of the actual message content.
Does not cover non-mechanical methods of frequency synchronization.
Does not cover the use of radio waves for anything other than remote control of a torpedo.
Who is building on this today
Major telecommunications companies like Qualcomm and Ericsson have built their entire business models on the evolution of spread-spectrum technology. The concepts pioneered here are now standard in every mobile network operator's infrastructure.
Products built on expired version of this technology
Modern Wi-Fi routers
Bluetooth device pairing
Military secure radio communications
GPS signal transmission
How to cite this patent in your documentation
Individual. US Patent 2292387. Secret communication system. Granted 1942, expired 1961. 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.