123456789 wrote in :

On 2/17/2019 8:56 PM, nospam wrote:

there was once a time when you couldn't do that in your own home. the
phone company only allowed their phones, even with rj11 jacks, and they
could tell if there were additional extensions you weren't paying for,
which is why many phones were designed to not be detectable.

The ringer on each phone/device puts a load on the line. If that load gets
too big the ringers won't work properly and other bad things micht occur.
That's what the big fuss was about with Ma Bell. They decided that the best
way to keep that from happening was to control the devices connected to the
line. These days, every landline device has a ringer equivalence number on
the label. The sum of all connected devices should not be greater that
four, if I remember correctly.