Having set up as lastly advised by Eric, the problems seemed to have vanished. As that time I was running my connection from the hard wired extension: telephone socket > filter> router, ignoring the surge protector. Now I have once more included the protector in the run, as in attachment, method #2 inclusive of filter, but no phone is linked to the filter, as the phone is a slave.
It may be entirely coincidental, yet invalid floating point errors, and DSLStats has stopped warnings have bloomed. Also the Systray then contains more than one icon!
Not direcly to do with this. I rebooted computer this evening, and reset the router, which had been suffering “No DSLConnection” problems. Here is the Event Log afterwards
08 May 2017 20:17:42 Recording started
08 May 2017 20:17:46 Impossible upstream ES value reported. Value set to zero.
08 May 2017 20:17:46 Impossible downstream ES value reported. Value set to zero.
08 May 2017 20:18:00 Unable to determine IP address
08 May 2017 20:18:14 DSL connection dropped
08 May 2017 20:18:14 No DSL connection
08 May 2017 20:18:45 DSL connection restored
08 May 2017 20:20:44 DSL connection dropped
08 May 2017 20:20:44 No DSL connection
08 May 2017 20:21:14 No DSL connection
08 May 2017 20:21:45 DSL connection restored
08 May 2017 20:21:49 IP address is now 91.125.*.*
Is it, then, mere coincidence, that the problems have resurfaced with the new configuration. I cannot see how it cannot be, or what more could be the problems.