Having been plunged into another installers project at short notice I have to connect Somfy to C4 using the RS485 RTS Transmitter device.
The driver indicates the following:
For device control, a RS23 to RS485 converter is required. This device has a 4 wire (NC, +, -, G) RS485 connector. Control requires only the use of the + and - wires. These two wires must be terminated to 120Ω resistors on the both the converter and transmitter ends.
Can anyone explain the 120 Ohm resistors and how to fit them? perhaps a small diagram?
Very much appreciated in advance.
Thanks
Mark