This circuit was found in the November 1992 issue of Radio Electronics magazine. The circuit has an amplification stage for the relay. The relay is rated at 12 V.
This reader with TTL logic compatible output uses an LM139 comparator. The circuit was found in...
This circuit can be used with common transistors, from general purpose to medium power. The...
Although it is a common configuration today, these circuits were taken from an old publication. The...