When I was young, no household had TWO phones; too expensive. We had a gadget that clipped on the phone earpiece and had an “extension” earpiece a few feet away connected by a rubber hose of about 3/8 inch diameter. The 2nd party held that to his ear (it was acoustically coupled; no electronics) and could hear the conversation just fine. Of course, he had no mouthpiece, but he was close enough to the main unit for that to pick up a word or two.
And my first phone didn’t have a coiled cord, but a straight one that kinked a lot and didn’t go very far. The handset weighed a ton and was hard-wired to the wall.
In this rural part of the country, all local phone numbers only required dialing the last 5 digits, and everyone knew the first of the five was a “3,” so when you told someone your phone number, you only gave the last 4.
Then when answering machines came in in the 1970’s, I bought one for $600 that was the size of a typewriter. The phone company gave me shit about connecting it to the phone lines and wanted me to install (and pay for) some kind of isolation device. I refused, and they dropped the request, since a challenge was making it thru the courts about that time.
I really hated dropping my human answering service, but $600 was cheaper than they were over a year or so.
The only nice thing about the answering machine (which could not be operated remotely) was the outgoing message tape, a loop. There was a metal foil strip applied to the back of the 1/4 tape to make it stop, and I was able to splice about 8 different messages into the cart, each with a foil strip at the end. So each caller got a different message. I had friends record some and put different music with some. Unfortunately, when someone called and heard the clever message (quite new at the time), they told all their friends to call and listen, too, but none of them got the same message! It tied up my line quite a bit.
I broke into the machine and modified the circuit so I could control how many rings it would answer on, from 0 to 6. It just involved changing a fixed resistor to a variable one and mounting it on the front panel.