circa 1988 and we were both into serial programming. He wrote a program that would answer the phone on one line with a modem, let the caller pick a target BBS, then it would dial out on another modem to connect to the BBS. Unlike the other solution it tied up two phone lines on the relay for the whole length of the call but it never redirected people who weren't expecting to be redirected.
https://www.old-computers.com/museum/computer.asp?c=1211
circa 1988 and we were both into serial programming. He wrote a program that would answer the phone on one line with a modem, let the caller pick a target BBS, then it would dial out on another modem to connect to the BBS. Unlike the other solution it tied up two phone lines on the relay for the whole length of the call but it never redirected people who weren't expecting to be redirected.