Originally designed to trigger a printer with a delay, this circuit can be used for other purposes. The circuit is from a Radio Electronics from September 1984.
This reader with TTL logic compatible output uses an LM139 comparator. The circuit was found in...
This circuit was found in an American documentation from the 80s. The transistor can be any...
The power supply for this circuit must be symmetrical at 12 + 12 V and the load must be 8 ohms. The...