Until recently, Alexander Graham Bell, who started work on a method of transmitting several signals simultaneously over a single wire called the harmonic telegraph in 1872, was credited with the invention of the telephone in 1876. However, it is now accepted that Antonio Meucci, an immigrant from Florence, invented the telephone in 1849 and filed a notice of intention to take out a patent in 1871. Unfortunately, Meucci was unable to pay the patent fees he abandoned the project. A later lawsuit against Bell revealed that he had worked in the same laboratory at Western Union Telegraph Company that had a model of Meucci's invention and its designs. In 2002 the US Congress righted the wrong and recognized Meucci as the inventor of the telephone. 

Although the first telegraph systems operated from point-to-point, the introduction of the telephone led to the development of switching centers. First-generation of switching centers employed a telephone operator who manually plugged a subscriber's line into a line connected to the next switching center in the link. By the end of the 19th century, the infrastructure of computer networks was already in place.

 In 1897 an undertaker called Strowger was annoyed to find that he was not getting the trade he expected because the local telephone operator was connecting prospective clients to Strowger’s competitor. So, Strowger cut out the human factor by inventing the automatic telephone exchange that used electromechanical devices to route calls between exchanges. When you dial a number using a rotary dial, a series of pulses are sent down the line to a rotary switch. If you dial, for example "5", the five pulses move a switch five steps clockwise to connect you to line number five that routes your call to the next switching center. Consequently, when you phoned someone using Strowger’s technology the number you dialed determined the route your call took though the system.

 By the time the telegraph was well established, radio was being developed. James Clerk Maxwell predicted radio waves in 1864 following his study of light and electromagnetic waves. Heinrich Hertz demonstrated the existence of radio waves in 1887 and Marconi is credited with being the first to use radio to span the Atlantic in 1901. 

The light bulb was invented by Edison in 1879. Investigations into its properties led Ambrose Fleming to the invention of the diode 1904. A diode is light bulb surrounded by a wire mesh that allows electricity to flow only one way between the filament (the cathode) and the mesh (the anode). The flow of electrons from the cathode gave us the term “cathode ray tube”. The diode was used in radios to detect radio waves.

 In 1906 Lee de Forest invented the triode vacuum-tube amplifier. De Forest’s device, called the Audion, was an extension of Fleming’s diode. It contained a wire mesh between the filament (cathode) and anode of Fleming’s diode. By changing the voltage on this mesh or grid, it was possible to change the flow of current between the cathode and anode. Without a vacuum tube (or transistor) to amplify weak signals, modern electronics would have been impossible. In general, the term electronics is used to refer to circuits with amplifying or active devices such as transistors. The first primitive computers using electromechanical devices did not use vacuum tubes and, therefore, these computers were not electronic computers.

 The Lee de Forest Audion 

In the late 1930s a Bell Telephone electromechanical calculator was connected to the telephone system and operated remotely by a Teletype – this was, you might say, the first example of remote computing.

 The telegraph, telephone and vacuum tube were all steps on the path to the development of the computer and, later, computer networks. As each of these practical steps was taken, there was a corresponding development in the accompanying theory (in the case of radio, the theory came before the discovery).