{ "schemaVersion": "1.0.0", "records": [ { "id": "history:mercadier-bi-telephone", "slug": "mercadier-bi-telephone", "title": "Two ears, hands free: Mercadier’s bi-telephone", "date": "1891-06-16", "sortYear": 1891, "era": "Communication", "people": [ "Ernest Jules Pierre Mercadier" ], "organizations": [], "device": "Bi-telephone, US454138A", "summary": "An 1891 patent documents paired ear receivers held by a resilient yoke.", "problem": "The patent addresses securing telephone receivers while leaving the operator’s hands free.", "solution": "Two receiver housings attach to a spring-like support; rubber-covered earpieces sit at the ears.", "significance": "This is direct evidence of a wearable, two-ear electrical listening design before Baldwin’s later devices.", "uncertainty": "A patent grant dates a documented design. It does not prove the first invention, commercial adoption or stereo reproduction.", "sources": [ { "url": "https://patents.google.com/patent/US454138A/en", "title": "US454138A: Mercadier bi-telephone", "type": "patent", "verifiedAt": "2026-09-27", "confidence": "primary-source", "scope": "Supports the stated facts; not independent performance testing." } ], "technologyIds": [], "predecessorIds": [], "successorIds": [], "imageStatus": "No cleared reproduction; view the source collection." }, { "id": "history:baldwin-type-c", "slug": "baldwin-type-c", "title": "Baldwin’s Type C in the museum record", "date": "1915–1920", "sortYear": 1915, "era": "Radio", "people": [ "Nathaniel Baldwin" ], "organizations": [ "Baldwin Radio Company" ], "device": "Type C headset", "summary": "A surviving Type C headset connects headphone history to radio communication.", "problem": "Radio and communication are the contexts recorded by the museum; the maker’s personal motivation is not established here.", "solution": "The Henry Ford preserves a Baldwin Radio Company headset made in Salt Lake City, dated 1915–1920.", "significance": "The object gives the timeline a physical reference, rather than relying on a single-inventor origin story.", "uncertainty": "Its inscriptions cite patents dated 1910 and 1915. Those dates are distinct from the museum’s manufacture range.", "sources": [ { "url": "https://www.thehenryford.org/collections/explore/artifact/234315", "title": "The Henry Ford: Type C headphones, 1915–1920", "type": "museum", "verifiedAt": "2026-09-27", "confidence": "primary-source", "scope": "Supports the stated facts; not independent performance testing." } ], "technologyIds": [], "predecessorIds": [], "successorIds": [], "imageStatus": "No cleared reproduction; view the source collection." }, { "id": "history:koss-sp3", "slug": "koss-sp3", "title": "Stereo music becomes a headphone proposition", "date": "1958", "sortYear": 1958, "era": "Stereo", "people": [ "John C. Koss", "Martin Lange Jr." ], "organizations": [ "Koss" ], "device": "SP/3 Stereophone", "summary": "Koss dates the SP/3 stereophone to 1958.", "problem": "Koss’s retrospective places the device within a stereo phonograph demonstration.", "solution": "John C. Koss and Martin Lange Jr. developed a portable stereo record player; the SP/3 became part of this music-listening story.", "significance": "The milestone shifts the timeline’s focus from communication to personal stereo music.", "uncertainty": "Koss calls it the first stereo headphone. We attribute that priority claim to the manufacturer rather than treating it as independently settled.", "sources": [ { "url": "https://koss.com/blogs/news/headphone-school-first-koss-sp3-stereophone", "title": "Koss: SP/3 history", "type": "manufacturer", "verifiedAt": "2026-09-27", "confidence": "primary-source", "scope": "Supports the stated facts; not independent performance testing." } ], "technologyIds": [], "predecessorIds": [], "successorIds": [], "imageStatus": "No cleared reproduction; view the source collection." }, { "id": "history:sennheiser-hd414", "slug": "sennheiser-hd414", "title": "An open-back milestone: HD 414", "date": "1968", "sortYear": 1968, "era": "Acoustic design", "people": [], "organizations": [ "Sennheiser" ], "device": "HD 414", "summary": "Sennheiser dates the launch of its HD 414 open-back headphones to 1968.", "problem": "The documented innovation concerns enclosure design, not a new recording format.", "solution": "The HD 414 introduced an open headphone construction in Sennheiser’s product history.", "significance": "It is a useful historical anchor for understanding open-back designs in today’s catalogue.", "uncertainty": "The world-first claim is Sennheiser’s account. This entry does not independently resolve all earlier experimental designs.", "sources": [ { "url": "https://newsroom.sennheiser.com/our-history-296431", "title": "Sennheiser: Our history", "type": "manufacturer", "verifiedAt": "2026-09-27", "confidence": "primary-source", "scope": "Supports the stated facts; not independent performance testing." } ], "technologyIds": [ "technology:open-back" ], "predecessorIds": [], "successorIds": [], "imageStatus": "No cleared reproduction; view the source collection." }, { "id": "history:sony-walkman", "slug": "sony-walkman", "title": "Stereo leaves the living room: TPS-L2", "date": "1979-07", "sortYear": 1979, "era": "Portable", "people": [], "organizations": [ "Sony" ], "device": "Walkman TPS-L2", "summary": "Sony’s first-generation Walkman went on sale in July 1979.", "problem": "Portable personal listening is the context of this milestone; no undocumented inventor motivation is assumed.", "solution": "The TPS-L2 paired a portable cassette player with headphone listening. Sony records different early overseas product names.", "significance": "The entry connects portable sources to the role of headphones in everyday listening.", "uncertainty": "July 1979 refers to the initial launch, not every regional release. The Walkman did not invent headphones.", "sources": [ { "url": "https://www.sony.com/en/SonyInfo/CorporateInfo/History/capsule/20/", "title": "Sony: Walkman time capsule", "type": "manufacturer", "verifiedAt": "2026-09-27", "confidence": "primary-source", "scope": "Supports the stated facts; not independent performance testing." } ], "technologyIds": [], "predecessorIds": [], "successorIds": [], "imageStatus": "No cleared reproduction; view the source collection." }, { "id": "history:bluetooth-le-audio", "slug": "bluetooth-le-audio", "title": "A new wireless audio specification family", "date": "2022-07-12", "sortYear": 2022, "era": "Wireless", "people": [], "organizations": [ "Bluetooth SIG" ], "device": "LE Audio specifications", "summary": "Bluetooth SIG announced completion of the LE Audio specification suite on 12 July 2022.", "problem": "The standard addresses audio delivery over Bluetooth Low Energy.", "solution": "LE Audio defines a new audio architecture, including the LC3 codec and multi-stream capabilities.", "significance": "It creates a standards milestone for later compatible headphones and source devices.", "uncertainty": "Specification completion is not a product launch. A Bluetooth version number alone does not establish LE Audio support.", "sources": [ { "url": "https://www.bluetooth.com/press/completion-le-audio/", "title": "Bluetooth SIG: completion of LE Audio specifications", "type": "standards-body", "verifiedAt": "2026-09-27", "confidence": "primary-source", "scope": "Supports the stated facts; not independent performance testing." } ], "technologyIds": [ "technology:bluetooth-le-audio" ], "predecessorIds": [], "successorIds": [], "imageStatus": "No cleared reproduction; view the source collection." } ] }