Found in a 1964 Electronic Design, this circuit uses a common LDR and transistors from that time. The relay is a high sensitivity type.
This two-digit digital pressure gauge was found in the 1992 special edition of Radio Electronics...
This circuit allows you to use a digital multimeter as a thermometer. The sensor is mounted in a...
We found this circuit in the Radio Electronics magazine of January 1986. The frequency is given by the...