You can freely build on How the First Wireless Television Remote Control Works
This patent expired in 1977. 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
Zenith Radio Corp
Patent granted
1957
Expired
1977
Forward citations
30
What this patent covers
The patent describes a remote control system that uses ultrasonic sound pulses to trigger specific functions on a television set. The remote contains mechanical hammers that strike aluminum rods of different lengths when a button is pressed, creating high-frequency sound waves above the range of human hearing. A microphone on the television receiver captures these specific frequencies, which are then converted into electrical signals to perform actions like changing channels or adjusting volume.
What is now free to use
All 0 claims of US 2817025 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 infrared (IR) remote controls, which use light pulses rather than sound waves.
Does not cover Bluetooth or Wi-Fi based remote controls.
Does not cover systems that require a direct electrical wire connection between the remote and the TV.
Does not cover digital signal processing or complex data transmission protocols.
Who is building on this today
While the ultrasonic technology was eventually replaced by infrared and later radio frequency (RF) standards, the design principles for user-interface remotes were pioneered by Zenith. Today, companies like Samsung, LG, and Sony build on the legacy of intuitive, wireless control interfaces.
Products built on expired version of this technology
Zenith Space Command 400 remote control
Early ultrasonic TV tuning systems
How to cite this patent in your documentation
Zenith Radio Corp. US Patent 2817025. Control system. Granted 1957, expired 1977. 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.