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.
This Circuit diagram presented in this schematic is an simple, low-cost, and easy to construct infrared remote control tester. The remote control tester circuit is built around an easily available infrared receiver module (TSOP 1238).