You can freely build on How the Frying Pan Guitar Created the Electric Guitar
This patent expired in 1954. 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
ELECTRO STRING INSTR CORP
Patent granted
1937
Expired
1954
Forward citations
24
What this patent covers
The patent describes an electrical stringed instrument that captures the vibrations of metal strings using a magnetic pickup. This pickup consists of a coil of wire wrapped around a magnet, which creates a magnetic field. When the metal strings vibrate, they disturb this field, inducing an electrical current in the coil that can be amplified by an external speaker. This design allowed guitars to finally be heard clearly in loud big-band settings.
What is now free to use
All 0 claims of US 2089171 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 acoustic guitars that rely solely on a hollow body for sound amplification.
Does not cover modern digital modeling or MIDI-based guitar synthesis.
Does not cover piezo-electric pickups that rely on physical pressure rather than magnetic induction.
Who is building on this today
Major manufacturers like Fender, Gibson, and Ibanez continue to refine the basic magnetic pickup design established by this patent. While the core technology is now public domain, these companies focus on material science and coil winding techniques to alter the tonal characteristics of the output signal.
Products built on expired version of this technology
Rickenbacker A-22 Frying Pan
Modern electric guitars from Fender and Gibson
Electric lap steel guitars
How to cite this patent in your documentation
ELECTRO STRING INSTR CORP. US Patent 2089171. Electrical stringed musical instrument. Granted 1937, expired 1954. 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.