Western Telematic Data/FaxModem - Manual (Page 6)

4. Installation
4.1. 48 Volt DC Power Option
The 48 Volt DC input is not polarity sensitive. Therefore, you can
connect either positive or negative wires from your 48 volt power
source to either input and the internal circuitry will adjust for the proper
polarity.
Input Range: 40 - 60 Volts DC, 200 milliamps maximum.
Page 4
RMM User’s Guide
Figure 3: 48 Volt DC Power Option