On Fri, 11 Dec 1998 10:16:10 -0800, thirdperson wrote:

>The SU-4 is a hot-shoe type device slightly bigger than, say, an AS-15 or
>AS-10. It attaches to the foot of the slave flash. It communicates with
>the camera using infrared signals, not light. [......]
>Please remember that I'm guessing about some of the above information.
>Also, neither product has shipped yet in the U.S.

Hmmm, a friend just got one, so I'm guessing they are in US,
and, far as he can tell (I haven't seen it...), it does work
by sensing when the main flash fires and shuts down (light
activated, which makes it awkward to use with other people's
flashes operating in the same room [making IR operation
preferable...]).