Found in a 1967 Ferranti documentation, this regulator makes use of an operational amplifier of the time. The output current is only 5 mA.
This circuit was found in Electronics Handbook, Vol XIII 1993 and consists of a simple direction...
This circuit works only with carbon microphones, due its low impedance. The speaker should be good or...
This is the normal circuit of a relaxation oscillator using an unijunction transistor such as the...