//dirt cheap wireless TX
//generates 38kHz carrier wave on pin 9 and 10
//sends data via TX every 500ms
void setup()
{
  pinMode(9, OUTPUT);
  pinMode(10, OUTPUT);

  // Clear Timer on Compare Match (CTC) Mode
  bitWrite(TCCR1A, WGM10, 0);
  bitWrite(TCCR1A, WGM11, 0);
  bitWrite(TCCR1B, WGM12, 1);
  bitWrite(TCCR1B, WGM13, 0);

  // Toggle OC1A and OC1B on Compare Match.
  bitWrite(TCCR1A, COM1A0, 1);
  bitWrite(TCCR1A, COM1A1, 0);
  bitWrite(TCCR1A, COM1B0, 1);
  bitWrite(TCCR1A, COM1B1, 0);

  // No prescaling
  bitWrite(TCCR1B, CS10, 1);
  bitWrite(TCCR1B, CS11, 0);
  bitWrite(TCCR1B, CS12, 0);

  OCR1A = 210;
  OCR1B = 210;

  Serial.begin(2400);
}

void loop()
{
  Serial.println("testing testing testing");
  delay(500);
}

via http://tinyurl.com/ir-remote-control

To decode what the remote was sending, I used an oscilloscope and a small photodiode. The photodiode generates a small amount of voltage when light hits it, and responds to changes in light level quickly enough that the oscilloscope can draw a really nice plot of the signal. I have a Parallax USB oscilloscope, which is perfect for showing the command pulses and is just fast enough to find the modulation frequency. As an aside, I’m really happy with the Parallax oscilloscope for projects like this. It is simple to use and I love being able to save images to share with people.
Here’s what two of the commands from the dimmer remote look like. The top signal is the “fade lights up” command, and the bottom one is “fade lights down”:

This scheme produces a sampled sine waveform with 12 samples per cycle. In addition to the desired frequency component, f₀, this waveform contains higher-frequency components at (12k+1)f₀ and (12k−1)f₀, k=1,2,3, and so forth. The lowpass filter comprising IC_2B, R₇, R₈, C₃, and C₄ easily filters out these undesired components of smaller amplitude. Listing 1 is the assembly-program code that implements the Bell 202 FSK standard. When the control input Data In is high, the output frequency is 1200 Hz; when the control is low, the output frequency is 2200 Hz. The transition from one frequency to the other occurs in a manner that retains phase continuity.

http://www.qsl.net/py4zbz/DSP/softw.htm "My first SDR is a software demodulator SSB (USB and LSB) with AGC, to be used in conjunction with a hardware SDR such as SDRZero. The I and Q signals produced by SDRZero are applied at the entrance of the stereo sound card, I being in the right channel and Q in the left. Comentarei, com ilustra ões feitas com o próprio BasicDSP, o programa exemplo. Comment, with ilustraões made with the very BasicDSP the program example."

""To make this usable as a modulator, the light from the laser arrives at the electro-optic modulator and is then split equally into two different paths. An electric field can be applied to each of these paths in order to shift the phase of the waves so that they arrive at the far end either in phase to give a pulse of light (a 1) or half a wavelength out of phase to give no light (a 0). You may also hear these devices referred to as Mach-Zehnder modulators. Lithium niobate is the material most commonly used in such a device.""

"Consumer IR, or CIR, refers to a wide variety of devices employing the infrared electromagnetic spectrum for wireless communications. Most commonly found in television remote controls, infrared ports are equally ubiquitous in consumer electronics, such as PDAs, laptops, and computers. The functionality of CIR is as broad as the consumer electronics that carry it. For instance, a television remote control can convey a "channel up" command to the television, while a computer might be able to surf the internet solely via CIR. The type, speed, bandwidth, and power of the transmitted information depends on the particular CIR protocol employed."

" NASA-SP-139 Price Code: A16 Keywords: DATA ACQUISITION MARINER SPACE PROBES MARS ENVIRONMENT COMPUTER PROGRAMS MARS ATMOSPHERE MARS SURFACE MISSION PLANNING SOLAR ORBITS SYSTEMS ANALYSIS TELEMETRY TRAJECTORY ANALYSIS Accessibility: Unclassified; No Copyright; Unlimited; Publicly available;"

The orginal is a Word. This is more convenient.