This CMOS circuit was obtained in a 1980s documentation. The circuit has a 10-second time delay before firing. The transistor is a general-purpose type and power supply according to the relay.
This receiver with two common JFETs was found in an old English documentation. The phone is...
This TTL circuit with the 7493 makes the binary count of the pulses sent by a flip-flop with the...
This circuit was found in a Popular Electronics from the 90s. The counter circuit is not common...