Campbell Scientific MD485 RS-485 Multidrop Interface - Manual (Page 27)

Appendix A. Phone to MD485 Network
COM220 and the base MD485 CS I/O port. Connect the site phone line
to COM220. Connect power to PS100. When you turn on the PS100
supply, the MD485 receives 12V power and you will see the LEDs light
in their power-up sequence.
Remote MD485s normally connect to datalogger CS I/O ports via SC12
cables. Powering up the datalogger will start the MD485 operating.
Connect the CABLE2TP cable between the RS-485 ports of the base and
remote MD485s and you are ready to connect to the datalogger.
A-5