Buzzers were used early on as a way to get ICW ( interrupted CW ) signals in early vacuum tube transmitters.
The buzzer would interrupt the CW at an audio rate, thus modulating the CW carrier.
Persian Army employs a relay system where soldiers positioned on hilltops shout and relay military messages 30 times faster than by runner.
Arc transmitters were brought to the United States in 1909. In Java, a unit was rated at 3,000 W, the antenna was suspended over a mountain gorge.DX is an early telephone term for distant exchange.It is also defined in Funk & Wagnall's as Distance.In the way of development after Marconi's high voltage spark gap came the use of high voltage transformers to generate the spark gap voltage. Here a 500 Hz generator, a step up transformer, and a rotary spark gap was used used to create the high voltage.The ultimate came in the powerful transmitters such as those at the U. Some of these produced a deafening noise created by the spark.