PLC to PLC connection via standard modem


Thread Starter


I am new in this kind of engeeniring and my question is maybe easy to solve, but I wonder how can I connect PLC to PLC via standard modems directly without any PCs. Problem is that my PLCs are far away from each other and i have just phone line. I know that my problem is connected with ASCII instuctions and configuration but i need detailled explanation. Thanks in advance
Please give more information. What PLC are you using? Yes, some PLC's can use a phone modem to communicate.
Yes, you can. How its done depends on which PLC's you are using. Check with the manufacturer for a communications manual. This is where you will find the detailed explanation you need. Main detail is if you have a regular phone line with a dial tone, or a leased line which already has the connection made. In the first case, your PLC will have to make a dial up connection to the other PLC.
What brand and model of plc are you using? If when you say standard modem you are talking cheap pc modem, yes you can, but it is often really difficult and you maust also askk should I use a commercial product to connect Industrial products and reduce the system reliability. For preconfigured modems for most plc brands look at "": there are configuration examples on the site, and they will be happy to help you solve your modem questions.

Hakan Ozevin

Siemens Simatic S7-200 with modem module. Very easy, cheap and off-the-shelf available with a configuration wizard. It can dial several numbers, have a password, callback, etc.
Yes, some PLC's can use a phone modem to communicate.
PLC is Allan Bradly slc5/03 os301, and I`m using cheep PC external modem. i need detailled explanation.