flipflop - BJT Astable Multivibrator

I have the basic knowledge about multivibrators, but I did not understand the working principles of the circuit schematic provided down below.

I have done the basic research about how it works, but I could not understand this particular BJT Astable Multivibrator circuit. Could someone please explain why 470 ohm and 10K ohm resistors are used and why the outputs of the circuit are not the emitter legs of the transistor but the collectors of the transistors.

And the most important question is : I put LEDs to the outputs. Does that changes the duty cycle of the Multivibrator (or frequency)?

Answer

The emitters of NPN bipolars are often directly connected to ground for various reasons. For one thing, this makes the circuit analysis easy. The NPN transistor starts conducting when there is more than about 0.7 volts base-emitter voltage. At that point the base-emitter current starts to flow, causing also the collector-emitter current to flow. As the emitter is connected to ground, you can see that this threshold voltage of 0.7 volts is 0.7 volts from the ground.

Consider T2. When a transistor's base has at least 0.7 volts, then the collector is drawing current, causing the collector voltage to be near zero volts. At that point, the LED D2 is not light. The other state is that the transistor is not conducting: at that point the LED is light and there is about 2 volts at OUT2. C2 charges to 1.3 volts : the left plate will have 0.7 volts (the threshold voltage of T1) and the right plate has 2 volts.

Now, let's say that T2 starts conducting. OUT2 will drop from 2 volts to 0 volts. But there is still 1.3 volts charged into the capacitor. This means that the left plate of C2 suddenly drops to -1.3 volts, causing T1 to stop conducting. C2 starts to discharge, C1 starts to charge.... and round and round we go.