The U.S. aircraft register, updated daily
Parts

Master Call

No failure report names the master call. 1 FAA approvals let 1 company make a replacement master call, Aaxico Technical Services holding the most (1).

Approved replacement parts 1 parts manufacturer approvals

A parts manufacturer approval (PMA) lets a company other than the aircraft's maker make a master call and sell it as an approved part for the models named. These are the companies holding such approvals for a master call:

For these models most: Boeing 777 (1).

MakerPartReplacesFitsGrantedStatus
Aaxico Technical ServicesMASTER CALL LIGHT ASSEMBLY 82000-38403ATSBOEING P/N S479W340-2, KOITO P/N 82000-38403BOEING 777F and 777-200, 200LR, 3002015-03-17current

Sources: the FAA's service difficulty reports since 1995 (a report is a part that failed and was fixed, as filed by an airline, repair station or owner; the count shows reporting as much as reliability) and the parts manufacturer approvals in the FAA's Dynamic Regulatory System. The part name is the reporters' and the approval holders' own words, reduced to the first plain words so that spellings meet.