When I was a young pup, we had loop lines in the Montreal area. If you've never heard of loop lines, they are special telephone circuits that were set up by the phone company for testing purposes. But word got out of their existence and the next thing you know, young single people are using them to meet new people.
Using them was fairly simple - each telephone prefix in the Montreal area had a loop line associated with it. I don't recall what the numbers were anymore, but let's say for example they were 1129 and 1130. If you called 473-1129, all you got was dead air, until someone called 473-1130. If two people happened to call the number pair at roughly the same time, you got connected. To a complete stranger. Hey, it was the 1970's. Protocol indicated that if you called and someone of the same sex was on the other line, one of you hung up so the other could wait for someone of the opposite sex to call the other side of the line.
I actually got up the nerve to meet someone that I met on the loop lines. We spent the night in downtown Montreal until sun-up. It was a pretty good date but that was it for that.