# How Radio Frequency Identification (RFID) Tags Were Invented > A 1970 patent describing a remote tag that powers itself using incoming radio signals to read and write data, forming the foundation of modern RFID technology. - **Patent:** US 3713148 - **Original title:** Transponder apparatus and system - **Owner:** Communications Services Corp Inc - **Granted:** 1973 - **Status:** Public domain (expired) - **Times cited:** 185 - **Field:** telecommunications, semiconductors, consumer_electronics ## What it does 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 it does NOT cover - 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. ## The clever bit The innovation was using the incoming interrogation signal not just for communication, but as a power source to energize the device, solving the problem of how to power a remote, battery-less sensor. ## Real-world examples 1. Electronic toll collection systems like E-ZPass 2. Contactless payment cards 3. Retail inventory tracking tags 4. Animal identification microchips 5. Building access control badges ## Why it matters This patent is widely considered the foundational document for RFID technology. It established the core architecture for passive tags used today in everything from inventory management and toll collection to secure building access and pet microchipping. ## Frequently asked questions ### What does How Radio Frequency Identification (RFID) Tags Were Invented cover? A 1970 patent describing a remote tag that powers itself using incoming radio signals to read and write data, forming the foundation of modern RFID technology. ### Who owns patent US 3713148? Communications Services Corp Inc owns this patent, granted in 1973. ### When does this patent expire? This patent has expired and is now in the public domain — anyone can use the invention freely. ### What is patent US 3713148 cited by? This patent has been cited by 185 later patents that build on its ideas. ### What problem does this patent solve? This patent is widely considered the foundational document for RFID technology. It established the core architecture for passive tags used today in everything from inventory management and toll collection to secure building access and pet microchipping. ### What does this patent NOT cover? Does not cover active transponders that rely on internal batteries for their primary power source. **Full plain-English explainer:** https://patentbrief.org/patent/us/3713148/rfid-transponder-cardullo **Original patent:** https://patents.google.com/patent/US3713148 --- _Source: PatentBrief — https://patentbrief.org. Patent facts are from public records; the plain-English explanation is PatentBrief's._ ## Related patents Semantically similar inventions in the PatentBrief corpus: - [How Early Cell Phones Handled Calls Across Different Towers](https://patentbrief.org/patent/us/3906166/cellular-mobile-phone-radio-telephone) — This patent describes a system for early portable phones to automatically find the strongest signal from a base station and switch channels as the user moves, reducing battery drain and interference. - [The Invention of the Modern Field-Effect Transistor](https://patentbrief.org/patent/us/3102230/mosfet-field-effect-transistor) — This 1960 patent describes the fundamental structure of the MOSFET, the tiny electronic switch that powers every modern computer processor. - [How Marconi Patented Early Wireless Telegraphy Signals](https://patentbrief.org/patent/us/586193/radio-wireless-marconi) — Guglielmo Marconi's 1897 patent for sending electrical signals through the air to enable early wireless communication. - [How to Create a Secret Code Key Without Meeting First](https://patentbrief.org/patent/us/4200770/diffie-hellman-public-key-exchange) — This 1980 patent describes a way for two people to create a secret code key over a public channel, like the internet, without ever meeting or sharing the key directly. - [How Mobile Phones Can Securely Authorize Payments Using Random ID Codes](https://patentbrief.org/patent/us/7577616/method-and-apparatus-of-secure-authentication-and-electronic-payment-through-mobile-communication-tool) — A 2006 system that uses a mobile phone to receive and relay a unique, temporary ID code to a store terminal to verify and authorize a payment transaction.