This 1974 circuit uses two 555 integrated circuits in a very traditional configuration. The circuit can be powered by voltages from 9 to 12 V and for greater volume an amplifier stage can be added.
This shield circuit was found in an American publication from the 80's. The triac is of low...
The Variable Frequency Oscillator (VFO) shown in the figure can generate signals in a frequency range...
This circuit was obtained from an 80's Radio Electronics. The circuit decodes “scrambled” or...