The DT80 logger is placed in a railcar to continuously measuring the temperature by thermocouple probes inside the refrigerator which is about -20C on the railcar. It sends the data through a modem to our ftp server so that we could remotely reads the temperatures. Since two days ago, we noticed that our thermocouple readings are "underrange" at the channels on CEM20 and "referror" on the main module. At this point, we are not able to access to the logger. What do you think could be the reason for these errors? Do you have an instruction for us to access to the logger remotely so that we could check the event log or reference temperature?