In order to connect to a device through a telephone modem, the modem must be configured to always dial and connect using the communication parameters that are defined in the PLC; otherwise, it will not be able to communicate with the device. Since most off-the-shelf modems are designed to provide internet access, they will not honor a configuration stored in Non-Volatile Random Access Memory (NVRAM). The Industrial Modems from Sixnet and the Z Modems from MultiTech work well for this setup.