This circuit is from a 1968 Electronics World. It acts directly on a high voltage alternating current relay. The sensor can be a common LDR.
This TTL divider divide by 0 to 9 the frequency of a signal applied to its input. Maximum...
Found in the American 73 magazine for radio amateurs, this circuit can test common quartz...
Found in a 1966 General Electric documentation, this circuit controls an incandescent lamp from an...