Frequency division multiplex (FDM)
A system in which the band of frequencies which may be transmitted on a common transmission path is divided into narrower bands, each used for a separate channel.
Reference: I.E.C. (modified)
Please note that this is the term as it stands in the original IALA Dictionary edition (1970-1989)
Celsius (previously Centigrade)
International Association of Marine Aids to Navigation and Lighthouse Authorities - AISM