In the construction industry, Tier 1 is a Contractor referred in ISO 19650 as the Lead appointed party, who provide goods or services directly to the ultimate client.
The Tier 1 are equivalent of the PAS 1192‑2:2013 lead suppliers

In the construction industry, Tier 1 is a Contractor referred in ISO 19650 as the Lead appointed party, who provide goods or services directly to the ultimate client.
The Tier 1 are equivalent of the PAS 1192‑2:2013 lead suppliers
Create unlimited lighting variations with advanced parametric control Introduction The
Asset management Overview principles and terminology The ISO 55000 standard
The rating factor Cs is applied to cable sizing calculations