I miss the simple days of computers and I attend to relive the past at times. I have a few old computers. Some of them have Dial-up modems that as we know are “useless” unless you know how to use them in the world of today. We’re in the digital age and most Analog is pretty much gone to a certain degree. For kicks I plan to setup a local private telecom exchange. To achieve this I will run a Linux host with a dial in server that will also be connected to the home network via Ethernet while a client system running for giggles Windows NT 3.51 that will connect to the host via a dial-up modem. Now how would someone make a analog modem connect with out the proper hardware? Simple, a circuit that will add the proper power to the line and simple AT commands if needed. Best from what I can tell I can make the host listen for the AT commands to connect and give a IP address to the client and then share the Ethernet connection. I don’t know exactly but I will find out. Might also give me a reason to host a old school BBS system.
The host will be my tinker system. Just need to toss in a extra hard drive and install Debian Linux. Also I will need to toss in a Dial-up modem. The client as said before will be running Windows NT 3.51 or maybe Windows 2000 Professional if I have too many hardware issues. The circuit for the phone line is a simple Line Simulator that uses a 500ohm resistor, .47uF cap and a 12volt power supply. Instead of using a wallwart I will use a unused 12 volt lead from the tinker system. It should be fine since the modems are isolated and also since it will not be connected to a real phone line I don’t have to worry about a power surge. However if a Wallwart is needed a 2200uF cap should be used on the positive and negative side to cut out the ripple from the AC voltage noise.
+ | | - 500 GREEN----------+---||||---/\/\/--+-------------RED | | | R | | 12V | | | +---||------------+ C .47uF RED-----------------------------------------------GREEN Be nice if I had a dumb terminal or even a teletype.