Modem Comms

If a plc has a serial port, is it possible to use a modem to remote view the plc? Id so what are the requirements?

I know this is a vague question bur would like know the rough theory first. I have seen it installed with AB SLC500s and Siemans S7300s but was never involved in its setup and the connection was never left in place.

If I can I am going to set this up at home using my trusty micologix1000 that I have tortured as a play projrct.

Thanks

sometimes you need telephone line, -number and modem to PLC end if there is RS232C in plc. As Simatic S7-300 see attached .jpg

The biggest problem is generally on the programming software end. Older versions of some PLC programming software didn't support dialing the modem and connecting. And many times if you used another communications or terminal program to do the dialing the PLC programming package wouldn't access the port because the terminal program had tied it up.

Most newer software for most PLCs will allow you to dial up over the modem and connect in easily. Check your software.

The second problem is that many PLC serial protocols require odd parity. Some modems won't support this. Again, check the software requirements and modem capabilities.

Guys, Im trying to inplment a step by step process for this because I ran into some probs.

1. Have a Micrologix series A
2. A modem that has auto answer(for micro).
3. Dedicated phone line for modem.
4. PC with RSlinx 2.2
5. Internal WinModem

Question, when setting up my driver in RSLinx Im not sure what to do.
My AB manuals that I have mention requirements of modem type etc
but I dont have the info on how to set up the driver.

As a guess Im using RS232 driver but my prob is how to configure the
modem driver in RSLinx? In my windows device manager it says my modem is using comm1 but when I select comm1 in the modem dialer tab of rslinx rslinx configures but tells me there is a resourece conflict.

Any ideas welcome please!