This tool is extremely useful for those working in development or repair of TTL logic circuits.
The logical end is fed from the same source voltage of the circuit under test, connect alligator (-) to the estate and the crocodile terminal (+) to positive 5 volts. The operation is very rudimentary and revolves around an NPN transistor that acts as a switch and three gates investors. There are only three possible states that may be present at the tip (marked Pta.).
In this case on the basis of the transistor there is no tension and therefore will not lead and at the entrance to the lower gate (terminal 5) has a logical low state, showing the gate opposite the value in its output (high state). This prevents the LED glows red. Returning to the tip (which was in low state), the entry gate of the upper left (Terminal 1) submit a logical low state, doing this in its output (terminal 2) a high state. This state means that, out of the second top gate (terminal 4) has a rule under which the wrong bicolor LED glows green, indicating a LOW state.
If the tip is a TTL high state the basis of this transistor component polarized and enter into what is driving the input of the gate will lower a logical high, which a state under a wrong exit and make The LED now glows in Colorado. As at the end there is a high out of the first gate will be higher under a state, making the second out of the gate is high. This will prevent the green LED lights up.
High impedance state (offline):
If you leave the tip anywhere without connecting the base of the transistor is not polarized, so (following the case of a low) the red LED does not glow. But as for TTL logic gates of a state of high impedance or off state is seen as a HIGH, the output of the gate top left is low, so that the output of the second gate will be high and the green LED does not glow . This means that when the tip is offline LED does not shine in any color.
Given the simplicity of the circuit can be mounted to the air within a small plastic tube and then you can fill with molten plastic. Also you can put on a universal printed circuit board. For positive and negative terminals is advisable to use crocodile clips and, for the entry of a signal test points or similar