Partylines existed in the UK during the 90s and 00s. They were a way for you to find out where the freeparty scene was happening. You would call up a number with a answerphone message and it would change as the night got later getting you closer and close to where the party actually was.

I had many a fond night, calling up waiting for the message to change.

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amenghra an hour ago | parent [-]

AFAIK, party lines were when N people were physically hooked up to the same phone line. All N people could talk to each other at the same time without dialing out/having to pay.

https://en.wikipedia.org/wiki/Party_line_(telephony)

	▲	patja 18 minutes ago \| parent [-]
		My family had a party line when I was growing up. The other parties who shared the line weren't very happy when 13-year-old me got his first 300 baud modem.