This is an how-to, not step by step guide (you need a minimal cisco router configuration skill), to set-up an little single PSTN line access router for your lab.
Is useful for testing and connect to a modern Internet BBS all kind of device with a old modem inside, like Videotel or Minitel terminal.

• 1 Cisco 1751-V Router with 1 VIC 2FXS interface
• 1 Cisco blue console cable, Rj45 - 9 pin female (part number 72-3383-01)
• 1 Cisco rs232 adapter 25 pin male - 9 pin male (part number 29-4043-01)
• 1 3Com U.S. Robotics 56K modem or any modem that support V.23 standard.
• 2 rj11 phone cable and an adapter for your videotel/minitel plug

use the rs232 adapter to connect the modem to the router's auxiliary port with console cable.
connect the modem line port to a router fxs port with rj11 telephone cable.
plug the videotel/minitel telephone cable to the other fxs port. you may need a rj11 adapter

V.23 in default modem configuration is disabled, you need to activate fallback with command ats27=16
and set the autoanswer with ats0=1
note: if you use another type of modem, registry settings for V.23 could be different

when the videotel terminal is connected to the aux port via modem, a raw telnet session is activated on a bbs server due the autoconnect command.
you can also decide to not do this and leave the router console at connection and start after the telnet command manually.
in this case remove autocommand line.

line aux 0
 login
 modem InOut
 autocommand  telnet bbs.retrocampus.com 23 /noecho /stream /quiet
 transport input all
 escape-character NONE
 databits 7
 parity even
 stopbits 1
 speed 1200

you can find a complete configuration example in repo

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