This simple 6 V source stabilized by zener diode was found in a European technical publication from 1972, but it is current for its simplicity and the components it uses.
This sensor circuit from a 1967 Ferranti documentation uses components from the era. The circuit...
This is the receiver for the previous circuit transmitter. Similarly, no information about the...
Found in a 90s Popular Electronics, this circuit uses two PLL tone recognizers to trigger by touch an...