Daylight Signal Light
A signal light exhibited by day and also, usually with reduced intensity, by night.
This reduction of intensity is made in order to avoid glare.
Daylight signals indicate, for example, whether the entrance to a lock is free or not.
Please note that this is the term as it stands in the original IALA Dictionary edition (1970-1989)
International Association of Marine Aids to Navigation and Lighthouse Authorities - AISM