2026-04-30
In 1970, a young inventor named Mario W. Cardullo filed a patent that would take over three decades to reach its full potential. US Patent 3,713,148, granted January 23, 1973, described a "Transponder apparatus and system" — a tiny, passive device that could receive a radio signal, use its energy to power itself on, and transmit back a unique identification code. No battery required.
The patent described a system with two components: an interrogator (a transmitter/receiver unit) and a small transponder that could store and relay data. Cardullo's key insight was that the transponder needed no internal power source. It harvested energy from the interrogator's radio signal, used that energy to activate its circuits, and reflected back a modulated response containing its stored information. The patent specifically described rewritable memory — the transponder could be updated with new data, not just read.
Cardullo initially pitched the technology to the Port Authority of New York for automated toll collection. His 1971 business plan proposed tagging vehicles with passive transponders that toll plazas could read at speed — eliminating the need to stop and pay. The Port Authority passed. The technology was, in their estimation, not ready for prime time.
They were right about the timing, but catastrophically wrong about the potential.
What Cardullo patented is what we now call RFID — Radio-Frequency Identification. The same fundamental principle powers:
The gap between patent and ubiquity is striking. Cardullo's 1970 filing described a complete, working system. But semiconductor manufacturing costs kept the technology confined to niche military and industrial applications for twenty years. It wasn't until the late 1990s that fabrication costs dropped enough to make disposable RFID tags economically viable. Walmart's 2003 mandate requiring suppliers to use RFID tags finally pushed the technology into mass production.
Today, over 30 billion RFID tags are produced annually. The tags themselves can cost under one cent each. The operating principle is unchanged from Cardullo's 1973 patent: harvest energy from an incoming radio signal, power on, transmit back stored data.
What's particularly prescient about Cardullo's patent is the rewritable memory specification. He didn't envision a static ID tag — he described a system where the transponder's stored information could be updated remotely. This is exactly how modern NFC works: your phone both reads and writes to transit cards, your building access permissions get updated without replacing the badge, and contactless payment tokens rotate with each transaction.
Cardullo saw an automated toll booth. He built the foundation for a world where physical objects carry digital identity — silently, passively, and without batteries — just by existing in the presence of a radio field.