[Doug] pulls a signal from the 9V AC power before it hits the bridge rectifier, using a 100K resistor and a zener diode to protect the microcontroller pin. The code for that project comes as a hex ...

He designed a transmitter to send and a receiver to detect radio waves. By the end of the century Marconi had managed to send signals over several miles with no wires, and the idea was taking hold ...

In an effort to achieve a faster and more attention-grabbing signal, delegates at the second International Radio Telegraphic Conference, held in Berlin in 1906, suggested a simpler signal -- SOS ...