Analog modem emulator?

Just curious...has there ever been a device available to anyone's knowledge that functions like an analog phone line and allows transmission via TCPIP? For example, taking an older BBS system that has 5 internal modems in it, and plugging the lines into this "mystery" device and then being able to telnet to different ports and it makes the connection to one of the ports? I've seen the UDS-10 device from Lantronix to emulate a serial modem, so essentially you can telnet to it from another PC and it fakes the computer into thinking someone's "ringing the phone, etc...but I want to take it one step back...leave the modems in place but emulate the phone lines. If it rings any bells, or if someone can think of a scenario this might be needed in, please drop me a note and maybe it'll help me track down something... Thanks! Pete