How to drive an X10 Firecracker (CM17A) using a RS232 module - Spider
The CM17A is a serial device that uses DTR and CTS to send the X10 commands. The RS232 module doesn’t have drivers for the DTR line. So by adding a jumper to the CM17A across pins 3 and 4 you can drive it with the TXD line. I adapted a driver written by Eddie Sheffield to use the txd line.