This 1967 Ferranti circuit uses company components. These transistors can be replaced by modern equivalents. The sensor is an LDR.
This amplifier, common in 1986, uses a hybrid integrated circuit that can offer some difficulty to obtain...
This is a simple voltage tester for voltages from about 2V to about 15V with the indicated...
This circuit was found in a publication from the 50's. The circuit uses germanium transistors of...