IDS: Can a Bypass Switch Prevent Link Flapping - When inline device fails?

[bikramkgupta () gmail com]

Hi,

I am looking at the following Net Optics Bypass switch.
http://netoptics.com/products/product_family_details.asp?cid=8&pid=214&Section=products&menuitem=8&tag=NetOptics+iBypass+Bypass

My initial understanding was that the Bypass switch will actually maintain link state with inline device, as well as, 
with external devices. And it will just switch the line when inline device fails.

But I do not see anything like that in the Net Optics Datasheet. My questions:

- How does an active bypass switch work, in physical or in data link layer?
- Is there any bypass switch in the market that can prevent link flap between external devices in the event of inline 
device failure? Does it make sense to have such a device?

Thanks a lot for your help.

Bikram