Primary sources anchor technical and regulatory claims. Product pages anchor competitor facts. Patents are flags for counsel, not legal conclusions. Every source has a use and a limit.
Primary modern feasibility anchor for passive piezo sensing, dual resonators, frequency-separated response, reader implementation, evaluation, cost estimate, and stated limitations. ACM DOI · author-hosted PDF.
Limit: research-grade, controlled conditions; not a neck-contact product, certified radio, production design, or license grant.
Primary institutional history: gift in 1945, discovery in 1952, passive operation, external radio illumination, diaphragm/resonant-cavity mechanism. NSA exhibit.
Limit: museum summary, not a complete engineering specification.
Prior analog backscatter speech architecture using a passive microphone, antenna modulation, and a base station. ACM DOI.
Limit: different topology and use case; does not validate the choker geometry.
Useful manufacturer guidance for 13.56 MHz loop modeling, inductance, Q, matching, measurement, and environment sensitivity. NXP PDF.
Limit: NFC product guidance; it does not establish continuous analog audio backscatter performance.
Intentional radiators generally require certification; Part 15 establishes technical and operating obligations. FCC explanation · eCFR Part 15.
Official overview that SRDs include RFID, telemetry, and wireless microphones and are subject to RED for EU market placement. ETSI.
Physical listening controls, observable recording, retention/deletion, access, sensitive voice data, and security-by-design. Voice assistant guidance · IoT security · Voice-data enforcement lessons.
Official product claims and current price/specification context for a rechargeable wearable meeting recorder. Plaud.
Recheck at every market review; price and claims change.
Official evidence that new Pendant sales ended in December 2025, support continues through 2026, and some regions lost service. Limitless.
Search family members, continuations, assignments, legal status, pending claims, and non-US jurisdictions. Read claims—not titles—and retain counsel.
sources.yaml records source type, date, URL, use, limitation, and freshness. claims.csv distinguishes demonstrated, derived, hypothesis, and blocked claims. Update both when facts or product pages change.