This circuit was found in a documentation of the 80s, having didactic purpose. For R1 values between 10k to 1M can be used. Transistors are general purpose types.
This circuit was obtained in an old American manual. The circuit is valid for any operational. The...
This two-relay circuit gives drive logic that is clear when analyzing the circuit. In the original...
This circuit, suggested by Philips Components (1980), uses a fast voltage comparator and requires...