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Throwback Thursday: First Electronic Device Ever Made, The Relay

The Relay machine, the first electronic device, is a remote switch-controlled device powered by electricity, created in 1835. The general consensus in the tech world is that it is the first-ever electronic device.


Two scientists share the credit of being the creators; Joseph Henry and Edward Davy.


An electronic device is one with components such as microchips and transistors that control and direct electric currents. A relay is simply a switch that uses electricity.


It is an early ancestor of every electronic device you know today. Before such things as the telephone and computer, there was the relay device.


Joseph Henry, an American scientist, designed the first one in 1935 as an improvement to his telegraph machine made in 1931. However, many sources also mention that Edward Davy had first made this machine in the same year.


The relay first electronic device
The relay device


Relays are used generally when it is important to control a high power or high voltage circuit with a low power circuit. The first application of relays was in long telegraph lines as we stated above already.


According to Circuits Today:


“A relay is an electromagnetic switch that is used to turn on and turn off a circuit by a low power signal, or where several circuits must be controlled by one signal.”

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In early telegraphs, the weak signal received at an intermediate station could control a contact, regenerating the signal for further transmission.


Major applications of the relay according to Circuits Today are:

  • A relay circuit is useful in realising logic functions. They play a very important role in providing safety critical logic.
  • Relays are important in providing time delay functions. They can time how long it takes to open and close contacts.
  • Relays control high voltage circuits with the help of low voltage signals. Similarly, they control high current circuits with the help of low current signals.
  • They are also useable as protective relays. By this function, it detects and isolates all the faults during transmission.

The relay, as the first electronic device, is important and credited with the birth of many modern inventions.


For example, Thomas Edison used the polarized (or polar) relay to make his quadruplex, which could send 4 simultaneous signals over a single wire. Also, Relays were important in early computers to perform logical operations. Some early calculators and computers also used relays.


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Onwuasoanya Obinna

A reader of books and stringer of words. Passionate about Science and Tech. When not writing or reading he is surfing the web and Tweeting.

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