Many thanks, thegeekway, for this info! That certainly is a good start.
I assume that one of these tx/rx pairs would work: http://www.robotshop.com/ca/433mhz-high-sensitivity-transmitter-receiver-pair-rxa33.html
I'm still confused, however, on how the Arduino sends the stop code to the mini-tx so the fan's rx can decode and execute it. If I read the referenced library correctly, it suggests attaching the handheld remote to the Arduino just long enough to store the code in the Arduino's memory. I assume that it will convert the code into some text form that I will then write into the Arduino's program. My intention is to thereafter detach the Arduino from the handheld and move it to the fan where it will reside permanently in a box above the fan body. Attached to the Arduino's output pin will be the input to the mini-tx. When an earthquake occurs, the Arduino will detect the event and send the stop code to the mini-tx, which will then broadcast it to the fan's built-in rx, which will then execute the command. The mini-rx that comes with the mini-tx/rx pair isn't needed as the fan's built-in rx will be retaining its normal functions. Is this the normal approach to solving these problems?
1. The fan's rx has dip switches that are used to change frequencies to avoid interference from other household devices. Is the mini-tx similarly adjustable?
2. Will the mini-tx convert the code to the proper modulation format or does the Arduino do this? If the latter, how do I make the Arduino do this?
I don't want to permanently attach anything to my handheld as that will "borgify" it to the point where it won't be used. The idea is to retain the original handheld as is and have the Arduino duplicate its stop code signal when an event occurs.
Again, many thanks for your help on this!