This circuit that imitates the sound of the cowboys' calls with their “louder” was found in a Hands On Electronics from the 80's. The integrated circuits used are from that time.
The output voltage is adjusted by the trimpot. The power transistor mist be mounted on a heatsink. The 3.9...
Originally, this circuit is from an English magazine, but I found it in Argentina's Radio Chassis...
The previously mentioned versions of monostable multivibrators in this section are not...