Eyc Headlight from B&M is part of my Brompton's Hub Dynamo lighting system.

Like this : B&M Eyc T Senso Plus Dyno Headlight

Eyc Senso T has 3 LED's 2 are day running lights , 1 the Bright one that shines down on the reflector , comes on from the Light sensor, at Night ..

the 'See By' Light.

so I Just leave it On and the engineering switches Modes for Me .