This circuit, obtained from a 1965 magazine, can still be assembled using some modern equivalent components. The transistors may be BC558 and the transformer is obtained from a disused transistor radio.
Originally this circuit is from an English magazine, but I found it in Argentina's Radio Chassis...
Figure bellow shows how n flip-flops can be associated to perform a shift register. Data is...
This other photodiode amplifier uses an operational amplifier in the non-inverting mode and in the...