George wrote:

Plugging a phone into the demark box doesn't mean he disconnected
the rest of his home's phone wiring from the box.

(a simple concept that some people around here want to keep fighting
over)

He must be a clever guy then and rigged up some Y cables or
something similar to cross connect the telco and premise sides
to defeat the purpose of the demarc.

The demark is the physical point at which the telco is responsible for
providing service or a connection point to the customer.

There is no standard specification as to how the customer's internal
premisis wiring is connected to the demarcation (in terms of detachable
plug vs hard-wired).

(rest of my post that George quoted for no reason deleted because I know
how to edit my usenet posts correctly)