This TTL tester device is very useful for viewing states TTL logic circuits. This TTL tester circuit can not be used to view states of CMOS circuits, since relatively high input current at leads will damage them clearly.
Device operation is very simple and requires no further explained LED "L" indicates the state of the input logic LOW, and LED 'H' HIGH state. Last LED indicates AC input signal and is very useful for detecting short pulses. The circuit senses the pulse of tens nanoseconds or even shorter.
Installation can be manufactured on a printed circuit board and incorporated in a pencil or a pen, where it connects with the aid of wires with clips to the checked power supply circuit or you can use an external 5 volts DC power supply .