On May 17, 2:52 pm, "JGalban via AviationKB.com" u32749@uwe wrote:
wrote:

I haven't yet seen a Continental or Lycoming lightplane engine
without an impulse coupling on at least one mag.

They're out there. In addition to the impuse system, there was a starting
system called "shower of sparks" that used a gadget called a vibrator to
provide the low rpm spark. Unlike the impulse system, the vibrator required
electrical power from the battery to make a spark.

I've usually seen these on older models.

Yup, you're right. Bendix made that system to provide a hot
spark for starting. The mag switch had extra terminals to provide an
AC signal from a buzzbox to the mag, but that mag had a second set of
points that gave the later spark for starting. Unison has a similar
setup now, but solid-state instead of an electromechanical buzzer to
create the signal for the primary winding.

Dan