In reply to a post by j0hn83:

I never said the Line loses sync when an OpenReach engineer runs WHOOSH tests.

I said they can, and do lose sync when am ISP runs an intrusive GEA test via KBD. Also known an E2E test.

KBD are tests which replaced the WHOOSH test suite for ISP's.

I'm no expert, but obviously neither are you with regards to ISP run tests, which is what the OP is asking about.

An ISP run test could cause the PPP session to drop.

But I stand by what I said. There�s no way ANY copper test being run via the test heads in the exchange would cause sync to drop. Even a Pair Quality Test can be run (by using the telephone port of an SSFP or microfilter) without VDSL sync dropping and a PQT is the most intrusive test that can be conducted if you think about it.