Campbell Scientific COM220 56k Phone Modem - Manual (Page 13)

COM220 Telephone Modem
FIGURE 3-2. CR10X with CR10 wiring panel and COM220 using
RJ11C telephone jack
3.2 Connecting to Earth Ground
Connect the green 14-AWG grounding wire (provided with the COM220) to
the ground terminal (GND) on the COM220 and to the enclosure’s earth
ground connection. If the site does not have a grounded enclosure, connect the
ground wire directly to an earth ground connection. The datalogger ground
should also be tied to the earth ground (see FIGURE 3-1 and FIGURE 3-2).
The modem must be grounded for its transient protection to
work.
CAUTION
14-AWG Ground Wire
Red
(+12V)
5