Remote access dial-up modem configuration

[blackbird307]

We have a customer that is having control system problems. They use a PLC that has been set-up for phone/fax remote access.

I have a US Robotics Sportster fax modem lying around. As soon as I try and connect to the PLC I get a message saying "Dialing", and then almost immediately after I get a message saying "Hang up". And this repeats 5 times until I get a message saying connection failed.

I think my modem may need to be configured.
There are some switches that correspond to stuff im not too familiar with and i was hoping if someone would be able to help me out.

1 :
UP = Data Terminal Ready Normal
Down = DTR Override

2 :
UP = Verbal request codes
Down = Numeric result codes

3 :
UP = Suppress result codes
Down = Display result codes

4 :
Up = Echo offline commands
Down = No echo, offline commands

5 :
UP = Auto answer on first ring or higher if specified in NVRAM
Down = Suppress Auto answer

6 :
UP = Carrier detect normal
Down = Carrier detect override

7 :
UP = Load NVRAM defaults
Down = Load factory defaults

8 :
UP = Dumb mode
Down = Smart mode

Current configuration
1 = up
2 = up
3 = down
4 = up
5 = up
6 = up
7 = down
8 = down

 

[Firejo]

You need to provide more detail.

What type of PLC are you using?

What communications protocol are you using?

Is the modem connected to the PLC and if so how is the PLC controlling the modem?

Between the “Dialing” and “Hang up” messages does the modem get an answer from the other end?

Most dial up modems configured for “consumer” use will hang up if you send data into the port prior to it finishing the handshaking process with its companion modem. Sometimes you can configure the modem to ignore anything coming into the port once it has dialed (until the carrier is established) however the best approach is to have the PLC not send any data until it sees the carrier detect signal from the modem.