Diode and resistor
We will now insert the diode, from the DCD pin of the serial port, to the voltage regulator, and the resistor from the cathode of the diode to the RTS pin.
You must cut the diode very short and insert the anode inside the 7th pin of the serial connector, which is photographed upside down in the picture:
After this you can easily solder the cathode of the diode with the input pin of the voltage regulator. Use the tweesers first to put it on the correct position and give a drop of solder.
We must cut in a similar way the resistor and solder it in the same place. We should leave the pins a bit longer because it must be inserted in the 1st pin of the serial connector: