If you have just set up your controller and it appears that you cannot send and/or receive X10 commands, here are a number of things you should check out:

The RJ11 cable

The cable between the controller and then PSC-05/TW-523 (I'll just call it the PSC-05 from here on, both units are equivalent) must be a straight, pin to pin cable and not a telephone cable, also known as a "rollover" cable. To know which one you have, hold the two ends pointing upwards and with both lock tabs towards you. The colors of the conductors must be the same from left to right, not a mirror image of each other. Even if your cable came with the controller, verify it anyways just to be absolutely sure. Look at the picture below:

The PSC-05's LED

The LED on the PSC-05 should stay lit when it is plugged into a live outlet. The LED will only blink "off" whenever a valid X10 command is being received my the module. When the module is sending X10, it also receives its own output, so the LED will also blink off whenever the module is successfully transmitting X10.

The controller's IR/X10 LED

The LED should normally be green if a PSC-05 is connected to the controller. This LED should become red whenever X10 commands are being sent or received by the controller. Any IR activity causes the LED to blink orange instead. On older controllers with single color LEDs, the LED will blink off instead of changing color.

Receive X10 tests

First, test that your controller can receive X10. Use an external device such as a minicontroller or a RF transceiver and a palmpad to send X10 commands to the powerline. Verify that the PSC-05's LED blinks "off" twice whenever you transmit a X10 command pair, indicating that the commands are reaching it over the powerline. The PSC-05's LED will blink off even if there is nothing connected to its RJ11 jack (so it can be used as convenient test receiver around the house too). Also verify that the controller's IR/X10 LED either blinks red or blinks off when you do this.

If the PSC-05's LED doesn't blink off, then you have a X10 signal quality issue. Often, this is caused by a "signal sucker" that is absorbing the signal, such as a laptop power supply, LED nightlight, poise filtering power strip, etc. You will need to resolve this problem before getting any furthur, but in the meantime try different outlets or unplug suspect signal absorbing devices until you can have it receive X10 successfully.

If the PSC-05's LED blinks off ok but the controller's LED doesn't change at all, then you likely have a bad/wrong RJ11 cable as explained above. Re-check it closely.

Now, use C-Max to attach to the controller and under the "X10" utilities, select "Monitor X10". Again, use your test transmitter to send X10 commands over the powerline and observe the monitoring window on the right side (check the "use names" box at the bottom). You should see the X10 signals that you sent appear in the column, with the most recent one at the top. For example if you used a minicontroller to send an A/1 On command, you should see:


If these tests work, then your controller is receiving X10 ok.

Transmit X10 tests

If the receiving test work ok, then try "Send X10" under the C-Max X10 utilities. utility...but close the "Monitor X10" window first! Nothing will get sent as long as that window remains open. Test transmitting by sending a command pair to turn on a light that you know works. The "Send X10" utility transmits single X10 commands, so you need to send two commands in order to make up a full command pair. For example, suppose that you want to turn on a light at address A/1: Click on radio buttons "A" and "1" and click on "Send". Then click on "A" and "On" and click on "Send" again. You should see the PSC-05 LED blink off each time you click on Send, and the light at that address should respond after the second command.

If the IR/X10 LED on the controller changes color (or blinks off) but the PSC-05's LED doesn't blink off at all, then you possibly have a problem with the RJ11 cable, or a X10 signal problem. Another less likely possibility is that you are experiencing the "weak power supply" issue with the PSC-05. To know if this is the problem, cup your hands over the PSC-05's LED so that you may observe it in the dark and then try to transmit X10 with your controller (you might need someone else to help you do this). If you see the PSC-05's LED dim very slightly instead of blinking off, then you might indeed be having this problem. Here is a thread that presents one modification that will often solve this problem: