Apple PowerMac G4 54k Modem Port U01.026.C.00 | eBay
This "Data" port found on the side of a hotel telephone. Must be a remnant of the early dial-up days where a modem was plugged in, connecting you to the internet. :
File:Modem creatix front.jpg - Wikimedia Commons
Build Your Own Dial-Up ISP – Now With Modem Pool! | Hackaday
V.90/V.92 54K PCI Voice External Data USB Fax Modem|fax pci modem|usb fax modem externalfax voice modem - AliExpress
54K Modem & ADSL Modem
HP 800G3EDD/I56500/128P/8C/54K US (2HH50US#ABA) at TigerDirect.com
5 Jahre Garantie auf heimische Produkte CPIMOP2014-01 Pctel PCI Modem Karte vergünstigter Ausverkauf -silverclippergrooming.com
Amazon.com: Actiontec USB 56K External Modem : Electronics
Leonix GSM Modem, Leo Electronics | ID: 15241810812
It's used as a modem on your side... - Vianet Communications | Facebook
USRobotics V 92 1 Port 56K Serial Controller Fax Modem Internet