No transients, no RF. It's that simple. However in the case at hand we are
more interested in zero current flow at switch time.

Bob Swinney
"Vaughn" wrote in message
...

"Robert Swinney" wrote in message
...
The point in time where a harmonic wave (can you say "sine wave")
intersects the ordinate, or "x" axis. Voltage is zero at that time thus
it is desireable for switching to occur at that time rather than earlier
or later. There can be no transient voltage at the time of zero crossing;
no chance of transient voltage damage to the switch.

I always thought the main reason for the zero switching was to reduce
generation of electrical/RF noise caused by switching. Back in my traffic
signal tech days, I used thousands of those things.

Vaughn