You hear it often: dating today doesn’t work like it used to. Or: apps like Tinder have made flirting more distant.

But the process of staring, judging, and messaging potential suitors from afar—hallmarks of modern dating apps—is not new. Beginning in the 1920s, nightclub-goers in Berlin who feared face-to-face encounters could communicate with beautiful strangers from across the room.

All they needed to do? Turn to the nearest pneumatic tube.

Two nightclubs in particular—the Resi and the Femina—pioneered the trend. At the Resi (also called the Residenz-Casino), a large nightclub with a live band and a dance floor that held 1,000 people, an elaborate system of table phones and pneumatic tubes allowed for anonymous, late-night flirtation between complete strangers.

A Chicago Tribune article describes the Resi’s “nightly ‘spectacular’—‘a dancing water ballet’ with jets of water rising and falling to a recorded symphony while colored lights flash.” The water-jet ballet, now known as a “Waltzing Water,” began in 1928 and drew in many visitors.

But the Tribune article refers to the system of phones and pneumatic tubes at each table as the Resi’s “big lure.”

Phones were fixed to individual tables, and above many was a lighted number. Singles needed only to look around the room until a fetching stranger caught their eye, note the number, and then direct a message to that table. “Lonesome Americans, and others, can call or send a note to equally lonesome women who look like they would enjoy company,” the article noted.

In 1931, during the heyday of this across-the-nightclub flirtation, The Berliner Herold described the process of receiving a call from an amorous stranger: “the tabletop telephones buzzed, and the acquaintance with the blonde, raven-haired or redheaded, monocle-wearing beauty was made, one was