Article 26

Every cycle shall be equipped with:
(?) At least one efficient brake;
(?) An audible warning device consisting of a bell, to the exclusion of any other audible warning device, capable of being heard at a reasonable distance;
(c) A white or yellow light in front and a red light or a red reflector in the rear from nightfall and during the night or when atmospheric conditions render it necessary.

 Convention of Road Traffic signed at Geneva September, 19 1949 (English)