The KR15A is a bizarre device. The ones I own have a date code sticker 00I38 and apparently a firmware sticker P10378D.
They work like this:
The "standard" X10 RF signals are 33 bits versus the 32 bits from other standard X10 RF devices, which probably accounts for the failure of some transceivers to properly decode them.
With a quick press of the button for no more than one flash of the LED, the device transmits:
Housecode|Unit ON
Houscode BRIGHT
If held for two flashes of the LED, the above plus:
Housecode DIM
Housecode BRIGHT
Housecode DIM
If held for three flashes of the LED, the above plus:
Housecode BRIGHT
Security PANIC
If held only until the LED comes on a fourth time, the above plus:
Housecode|Unit ON
Then 11 seconds later:
Security PANIC
Unless the button is tapped again, the LED stays on for over 2 minutes but with no further transmissions.
If held pressed after the LED comes on the fourth time, the whole sequence is:
Housecode|Unit ON
Houscode BRIGHT
Housecode DIM
Housecode BRIGHT
Housecode DIM
Housecode BRIGHT
Security PANIC
Housecode|Unit ON -> repeated every 4 seconds while the button remains pressed.
...
...
Then 14 seconds after the button is released:
Security PANIC
And the LED again remains on for over 2 minutes unless the button is tapped.
KR15A units with later date code stickers may behave quite differently.