You have limited options for turning on a module (A9) from another device (A8). As others have said, if you are using standard X10 switch modules, they don't send a PLC instruction when toggled. I have a few options that I have used to consider.
XPT - in wall transmitter. You can install it in a standard light switch box and depending on the cover have up to 4 addresses that you can send on/off or dim commands for.
Smart Home Toggle Linc - in wall switch that looks like a standard toggle switch. These will send X10 commands (if they still have the X10 address included in their firmware) when you toggle them on/off. I use one of these exclusively to send the X10 command that I have my HA software infer what to do (turn a light on, turn it on and set a timer, etc). There are also Switch Linc versions that use the decora style plate
Stick-A-Switch - RF version of the XPT option. Will send an RF signal for whatever address. If you have good RF coverage, this is a good option but may not look the greatest depending on your decor.
X10 mini controller - you could have a mini (or maxi) controller located where you want your switch and send the command manually. Not a great option for having guests understand how to use it.
Motion sensors - obviously, instead of having a switch you could just use a motion sensor module or motion sensor integrated light.