Found in a Popular Electronics from the 90s, this circuit uses components that are still current. The circuit triggers the vehicle's horn. The sensors can be increased in number.
The figure shows how to couple two CMOS circuits using an optical coupler to achieve isolation. The...
The Variable Frequency Oscillator (VFO) or Variable Frequency Oscillator shown in the figure can...
The circuit shown is from the National Semiconductor Linear Applications Handbook of 1994. using...