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.
We found the circuit of this Japanese transistorized commercial receiver in a documentation from...
In the figure we have a constant current source for Shape Memory Alloy or (Nitinol). The...
We found this circuit in the Texas Instruments opto-electronics manual. The button resets and the...