You can freely build on Lee De Forest's Early Radio Telegraphy System
This patent expired in 1927. 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
FOREST RADIO TELEPHONE CO DE
Patent granted
1908
Expired
1927
Forward citations
2
What this patent covers
This patent details a system for space telegraphy, which was the early term for wireless radio communication. It focuses on the hardware arrangement for generating and detecting electromagnetic waves across distances. By utilizing early components that would eventually evolve into the triode vacuum tube, the system allowed for the modulation of electrical signals to transmit information wirelessly through the air.
What is now free to use
All 0 claims of US 879532 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 modern digital signal processing or binary data transmission.
Does not cover the later invention of the Audion triode amplifier itself, which was patented separately.
Does not cover satellite-based communication systems or modern cellular networks.
Who is building on this today
Modern telecommunications companies like Qualcomm and Nokia trace their technical lineage back to these early radio transmission principles. The fundamental physics of signal modulation established here remains the bedrock of all wireless infrastructure.
Products built on expired version of this technology
Early wireless telegraphy stations
Pioneering radio broadcasting equipment
How to cite this patent in your documentation
FOREST RADIO TELEPHONE CO DE. US Patent 879532. Space telegraphy.. Granted 1908, expired 1927. 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.