You can freely build on How Radio Frequency Identification (RFID) Tags Were Invented
This patent expired in 1990. Every claim — 0 independent, 1 dependent — is now unenforceable. Anyone can use, reproduce, manufacture, sell, or offer for sale this technology without a license.
Original assignee
Communications Services Corp Inc
Patent granted
1973
Expired
1990
Forward citations
185
What this patent covers
This patent describes a transponder that acts as a remote data storage device. It uses an incoming signal from a base station to wake up, power its internal circuits, and either read or write data to its memory. Once the data is processed, the device sends an answerback signal back to the base station. By harvesting energy directly from the interrogation signal, the device eliminates the need for an internal battery, making it entirely self-contained.
What is now free to use
All 1 claims of US 3713148 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 active transponders that rely on internal batteries for their primary power source.
Does not cover systems where the base station does not provide the energy for the transponder's operation.
Does not cover non-electronic storage methods that do not involve a memory means capable of being written to or read from via signal processing.
Who is building on this today
Companies like NXP Semiconductors, Impinj, and Alien Technology have built massive businesses refining the passive RFID concepts outlined here. These firms continue to advance the efficiency of energy harvesting and data storage density for tags.
Products built on expired version of this technology
Electronic toll collection systems like E-ZPass
Contactless payment cards
Retail inventory tracking tags
Animal identification microchips
Building access control badges
How to cite this patent in your documentation
Communications Services Corp Inc. US Patent 3713148. Transponder apparatus and system. Granted 1973, expired 1990. 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.