On Wed, 14 Oct 2020 20:05:06 +0100, T i m wrote:

This is why I was unsure if there was a formal designation for this
base and wiring (two connections, one filament and not using the metal
of the cap as a (ground) connector).

B15d is bayonet, 15 mm, double
B15s is bayonet, 15 mm, single
(t triple, q uadruple, , p penta/five)

A is for automotive, Y yellow (though this rule seems often ignored).

And BAY15d may have different-height pins, with two base contacts and case for
ground, for double-filament automotive lights that need a single mounting
orientation (brake & running light, I think is one...)


Thomas Prufer