Taiyo Yuden Co., Ltd. is a Japanese electronics manufacturer that holds six IEEE MA-L (24-bit OUI) blocks: 00:03:7A, 00:22:58, 48:A4:93, 8C:D5:4A, AC:3F:A4, and D4:4B:5E — roughly 100.7 million addresses in total. While the company is best known for passive components (multilayer ceramic capacitors and inductors), the MAC assignments trace to its wireless connectivity business: Bluetooth Low Energy (BLE) and Wi-Fi modules built around Nordic Semiconductor nRF SoCs and embedded into IoT end-devices. Taiyo Yuden's own press releases place these modules in wearables, healthcare and medical monitoring equipment, and logistics terminals, so a device presenting one of these OUIs is far more likely an embedded BLE/Wi-Fi module than networking infrastructure. The critical caveat for asset classification: Taiyo Yuden transferred its entire Bluetooth and wireless LAN module business to Kaga FEI Co., Ltd. effective 2022-01-01 (announced 2021-10-14), and Kaga FEI now manufactures and supports the successor modules. IEEE block assignments are not re-registered on a business transfer, so all six OUIs remain in Taiyo Yuden's name even though post-2022 device support sits with Kaga FEI. The registry address on the newer blocks is 8-1, Sakae-cho, Takasaki-shi, Gunma 370-8522, JP; the corporate headquarters is in Chuo-ku, Tokyo. As with every IEEE OUI, no registration date is published — any "date registered" shown by third-party lookup tools is a database artifact, not an IEEE fact, and is recorded here as Unknown.
- IEEE assignment
- 6 prefixes → TAIYO YUDEN CO., LTD. [Confirmed] — IEEE MA-L (https://regauth.standards.ieee.org/standards-ra-web/pub/view.html#registries)
- Registry / block size
- MA-L (24-bit OUI); 6 blocks (~100.7M addresses). No MA-M or MA-S assignments found. [Confirmed] — IEEE oui.csv (enrichment/registries/oui.csv rows 121, 19716, 19787, 25479, 28139, 37401). NOTE: IEEE's public OUI data publishes NO assignment/registration date; any "date registered" on third-party tools (maclookup.app shows a 2000–2023 range) is a database artifact, not an IEEE fact.
- Verified prefixes (all MA-L, Taiyo Yuden)
- 00:03:7A, 00:22:58, 48:A4:93, 8C:D5:4A, AC:3F:A4, D4:4B:5E [Confirmed] — IEEE oui.csv / maclookup.app (https://maclookup.app/vendors/taiyo-yuden-co-ltd)
- Registry address
- 8-1, Sakae-cho, Takasaki-shi, Gunma 370-8522, JP [Confirmed] — IEEE MA-L (older 00:03:7A / 00:22:58 records list a shorter "8-1 Sakae-Cho, JP" form; same site)
- Country
- JP [Confirmed] — IEEE MA-L
- HQ note
- corporate headquarters in Chuo-ku, Tokyo; OUI registry address is the Takasaki-shi, Gunma site [Confirmed] — en.wikipedia.org/wiki/Taiyo_Yuden, maclookup.app/vendors/taiyo-yuden-co-ltd
- Company status
- active (operating; refocused on passive components after the 2022 module divestiture) [Confirmed] — https://www.yuden.co.jp/en/
- Device types
- wireless connectivity modules — Bluetooth Low Energy (BLE) and Wi-Fi modules embedded in IoT end-devices; confirmed target applications include wearables, healthcare/medical monitoring, and logistics terminals [Confirmed] — https://www.prnewswire.com/news-releases/taiyo-yuden-expands-its-product-lineup-of-bluetooth-5-wireless-communication-modules-300714213.html, https://www.yuden.co.jp/kr/product/category/module/bluetooth/EYSGCNZWY.html
- Notable products
- BLE module series (e.g. EYSGCNZWY, EYSGJNZWY) based on Nordic nRF SoCs [Likely] — single-source product pages (https://www.yuden.co.jp/kr/product/category/module/bluetooth/EYSGCNZWY.html)
- Business transfer
- Bluetooth + wireless LAN module business transferred to Kaga FEI Co., Ltd. effective 2022-01-01 (announced 2021-10-14); OUIs remain registered to Taiyo Yuden [Confirmed] — https://passive-components.eu/taiyo-yuden-transfers-its-wireless-module-business/, https://www.yuden.co.jp/cn/news/category/upload/211014en.pdf
- Registration date
- Unknown — IEEE publishes none; third-party dates are database artifacts [Unknown] — (no citation; IEEE oui.csv has no date column)
- IANA reference
- Unknown / not applicable — these are IEEE MA-L allocations, not IANA assignments; column left blank [Unknown] — (no IANA reference applicable)
- Security context
- no Taiyo Yuden-specific CVEs found. Modules use Nordic nRF SoCs and were sold for healthcare/wearable use, so deployed devices may handle sensitive biometric data; generic BLE protocol risks (MITM during pairing, BLE sniffing, malformed-L2CAP DoS) are inherent to the BLE stack, not Taiyo Yuden's implementation. The SweynTooth BLE vulnerability set (2020, CISA ICS-ALERT-20-063-01) did NOT name Taiyo Yuden among affected vendors. [Likely] — https://www.cisa.gov/news-events/ics-alerts/ics-alert-20-063-01, https://novelbits.io/sweyntooth-ble-vulnerabilities/
- Analyst note
- a Taiyo Yuden OUI on a globally-administered address indicates an embedded BLE/Wi-Fi module (IoT/wearable/healthcare class), not networking infrastructure; post-2022 hardware support belongs to Kaga FEI even though the OUI still resolves to Taiyo Yuden.