History of electronic engineering on to develop the first practical and widely used radio wave based communication system. In 1904, John Ambrose Fleming, the first professor of electrical Engineering at University College London, invented the first radio tube, the diode. Then, in 1906, Robert von Lieben and Lee De Forest independently developed the amplifier tube, called the triode. Electronics is often considered to have begun with the invention of the triode. Within 10 years, the device was used in radio transmitters and receivers as well as systems for long distance telephone calls. The invention of the triode amplifier, generator, and detector made audio communication
Zone valve spring but can be opened by the force of the wax motor. Removal of electrical power re-closes the valve. This style of zone valve operates with a perfectly ordinary SPST thermostat. For vacuum- or pneumatically operated zone valves, the thermostat usually switches the pressure or vacuum on or off, causing a spring-loaded rubber diaphragm to move and actuate the valve. Unlike the electrical zone valves, these valves automatically return to the default position without the application of any power, and the default position is usually "open", allowing heat to flow. Highly sophisticated systems may use some form of building automation