LED's pulsed for say 200% of their 'normal' current at a 50% duty cycle appear brighter than 100% current for 100% duty cycle even though the maths says that it's all the same average current. Remote controls are almost always pulsed. In fact, if you want to get more than a couple of feet covered, you almost *have* to pulse the IR LEDs. Note that since current in a series circuit is the same through all the series elements (non-reactive), you can string several LEDs in series and pulse the whole string using the same amount of total energy that you would have used to pulse just one. Instead of wasting the energy as heat in a resistor, you recover it as more usefil light from the LEDs. Multiple LEDs give you better 'coverage' than a single LED.

See also:

IR standards?

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