Ring protection is a system where multiplexers are connected in a ring topology. If a single span fails traffic switches around the other side of the ring.

nope, not with out protection or when you have a promise ring!

No there not same

If you used the ring correctly and consistently in the three weeks before the ring-free week, you have no decrease in protection during the ring-free week.

It is a retractor to provides exposure and wound protection to the incision.