Electrical/Electronic inventions that changed the world

Flip Flop Circuit : Eccles and Jordan (1918)

In 1918 British scientists William Henry Ecclesand Frank Wilfred Jordan invented the electronic circuit that would become the key building block for the development and advancement of electronic computers.

Eccles had pioneered the development of radio communication and assisted Guglielmo Marconi, and together with Jordan worked with leading edge electronic technology of the time, vacuum tubes, the predecessor of the transistor.

Eccles was a radio pioneer and his interest in vacuum tubes stemmed from their use in radio. In particular, the vacuum-tube ‘diode’ was used to detect radio signals indeed, the term “diode” was coined by Eccles.

Experimenting with vacuum tubes, Eccles and Jordan found a particular type of electronic circuit with an interesting property, … the circuit appeared to possess ‘memory’. Unlike other circuits whose output voltage levels would change depending on input voltage levels, i.e. operating in the analogue, ‘continuous’ time domain, this circuit operated in a ‘discontinuous’, digital manner having two stable discrete states.

Introducing a brief voltage ‘pulse’ to one of two input’s to the circuit, the circuit would ‘flip’ the state of the two outputs of the circuit to the opposite stable state. The circuit would remain in this condition until a further voltage pulse was applied to the opposing input, which would then trigger the circuit to ‘flop’ back into the original state.

The two output ‘flip and the flop’ states had distinct voltage levels which could be attributed to the discrete, ‘digital’ levels we now understand and refer to as ‘0’ and ‘1’. Consequently, the fundamental element of an electronic digital memory had been created and having no moving parts, this vacuum tube memory was much faster than its mechanical predecessors.

Vacuum tube flips-flop circuits were first introduced into service as computer memories just prior to World War 2, enabling a new electronic generation of computers to be prepared for service in the war effort.

The ‘flip flop’ circuit are now ‘transistorised’ and embedded within silicon packages in their millions forming the heart of computer memory and processors.


Eur Ing Dr Robert Brown (Robert) is the Executive Director of Fraser George and Associates Limited and is a Consultant Engineer in the fields Electrical Electronic and Control Engineering. Robert is also an accomplished professional Expert Witness having prepared and presented many court compliant reports and presented oral evidence within the High Court, Crown Courts and County Courts.

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