IR remote control has a limited range and doesn't work when it is out of line of sight. But what if you need to control your appliances even if don't see them. [Michail] suggest to build an IR remote extender that stands between your remote control and device to be controlled.

Multivibrator circuit is one of the first projects you start learning electronics. It is really wonderful circuit widely used for educational purposes and even in end projects as waveform generators. Lots of hobbyists simply grab a microcontroller/Arduino to blink LEDs. But using basic circuits like multivibrator may be cheaper, faster and even fun. [Ray] decided to go through multivibrator theory and explain its working in detail step by step.

Circuit itself consists of two transistors, two capacitors and four resistors. When powered, circuit generates square wave signal that can be used to flash LEDs, or clock other circuits. You will get an intuition on what causes multivibrator continuously generate. Formulas allow to calculate resistor and capacitor values for particular frequency. Especially if you are starter in electronics build one on a breadboard and do some experiments, why not to start wit Christmas lights.