said by n2jtx
:OTOH, before the breakup, doing your own wiring was generally prohibited by the telcos. Connecting more phones than you were renting was a violation (my folks used to rent two phones but we had a third one in another room that we always had to hide if the phone company came around).
They could have also found out you had multiple phones by looking at the amount of current your phone line drew from the CO. At least that's how my dad got busted when he "illegally" ran a phone extension (see post below).