Siemens Rail Automation SAU holds a single MA-L (24-bit OUI) block, 90:DA:F9, registered to the Spanish subsidiary at Ronda de Europa, 5, Tres Cantos, ES 28760 — in the Madrid metropolitan area. The "SAU" suffix marks a Sociedad Anónima Unipersonal, a single-shareholder Spanish legal entity wholly owned within the Siemens group; the company was formerly the Dimetronic signalling business and now operates as one of Siemens Mobility's competence centres for railway signalling. Hardware likely to carry this prefix is industrial OT/ICS equipment for safety-critical rail infrastructure: wayside signalling computers, electronic interlockings, ERTMS/ETCS trackside and onboard units, CBTC subsystems, ATC/ATO/ATS hardware, and traffic-control-centre workstations. The practical security consequence is that a device resolving to 90:DA:F9 should be treated as a critical-infrastructure OT endpoint governed by IEC 62443, not as general-purpose IT gear: interlocking computers, wayside-to-control-centre IP links, and radio-block-controller connectivity are all network-exposed surfaces, and CISA has flagged ICS advisories touching Siemens rail signalling products. As with all OUI work, IEEE publishes no registration date for this assignment — any "date registered" on a third-party MAC tool is a database artifact, not an IEEE fact.
- IEEE assignment
- 90:DA:F9 → Siemens Rail Automation SAU [Confirmed] — enrichment/registries/oui.csv (line 466), corroborated by rst.im/oui/Siemens
- Registry / block size
- MA-L (24-bit OUI), single block [Confirmed] — enrichment/registries/oui.csv. No MA-M (mam.csv) or MA-S (oui36.csv) entry found for this entity [Confirmed] — enrichment/registries/mam.csv, enrichment/registries/oui36.csv
- Registry address / country
- Ronda de Europa, 5, Tres Cantos, ES 28760 — Spain [Confirmed] — enrichment/registries/oui.csv; corroborated by D&B / Mafex listings
- Company status
- active; wholly-owned Siemens subsidiary, formerly Dimetronic (Invensys Rail Dimetronic group) [Confirmed] — dnb.com business directory, empresite.eleconomista.es, mafex.es
- Device types
- railway signalling and automatic train control equipment — wayside signalling computers, electronic interlockings (EI), ERTMS/ETCS trackside and onboard units, CBTC subsystems, ATC/ATO/ATS hardware, traffic-control-centre (CTC) workstations, communication/radio gateways, passenger-information and video-surveillance controllers [Confirmed] — mafex.es portfolio listing, mobility.siemens.com wayside control systems, railwaygazette.com (Tres Cantos signalling R&D centre, 2015)
- Industry
- rail infrastructure / signalling (industrial OT/ICS) [Confirmed] — mobility.siemens.com
- Registration date
- Unknown — IEEE publishes no registration/assignment dates for OUI/MA-L blocks; no date field exists in the registry CSV, and no first-party source was found [Confirmed that none exists] — enrichment/registries/oui.csv
- Vendor site
- https://www.mobility.siemens.com/global/en/portfolio/rail-infrastructure.html (parent Siemens Mobility division; the SAU has no standalone public product site) [Confirmed] — mobility.siemens.com
- Related vendors
- Siemens AG / Siemens Mobility (parent; holds separate OUI registrations distinct from the SAU entity); Dimetronic (predecessor)
- Security / analyst note
- devices on this OUI are safety-critical rail OT assets governed by IEC 62443. Siemens Mobility holds TÜV SÜD IEC 62443 certification for its Train Blueprint Architecture (ATC systems / onboard comms). Treat 90:DA:F9 endpoints as critical-infrastructure OT — interlocking computers, wayside-to-control IP links, and ERTMS radio-block-controller connectivity are network-exposed; CISA has issued ICS advisories touching Siemens rail signalling products. [Confirmed] — globalrailwayreview.com (TÜV SÜD cert), industrialcyber.co (CISA ICS advisories), mobility.siemens.com OT cybersecurity