One more thing, if you go shopping for a taillight that is of different manufacturer than your headlamp, there is at least one brand that is incompatible with other brands. Peter White covers some of that on this page under the topic compatibility.
Busch & Müller Taillights
Originally Posted by
znomit
Blinking is verboten under StVZO (German road traffic regulations), because its harder to judge distances.
- Lighting A white headlight and a red rear light are required and must be ready for use at any time. The headlight and rear light must be turned on with a single switch. They must be able to be powered by a dynamo backup, though they can use batteries in addition (as a standlight for example). One additional battery powered rear light may be added at the most; further battery powered lamps are not permitted, including blinking ones or ones on the helmet or body. Racing bikes (in Switzerland 700c x 23 or thinner) up to 11 kg weight (24.25 lbs or 12 kg/26.45 lbs in Austria and Switzerland) are not required to have the dynamo lighting, but may use removable battery powered lights. These lights must be carried at all times. All lighting needs an approval stamp from the German department of transportation in Flensburg - see the image at top or your own B&M LED lamps. Incidentally, the lights that are permitted don't have a setting for blinking. All lights stay on when switched on so that other traffic participants can judge distances well, something that is harder with a blinking light.
Thanks for posting. I was curious why all the dyno powered taillights I have seen are always wired to the headlight, and the requirement that both lights use a single on/off switch helps explain why.