Found in an American 1980s documentation, this circuit compares signals from two TTL sources, providing an output that depends on the frequency difference. The circuit can be used as a shield.
We find this circuit in an Electronic Design of the 90s. The used integrated circuit admits...
This circuit was originally designed for medical applications and biological experiments. The...
In this circuit of 1987 the player has to briefly press one of the keys trying to hit which LED...