{"id":11143,"date":"2026-08-22T22:25:51","date_gmt":"2026-08-22T20:25:51","guid":{"rendered":"https:\/\/3cxcloud.lt\/history-of-telephony\/"},"modified":"2026-09-20T23:05:23","modified_gmt":"2026-09-20T21:05:23","slug":"history-of-telephony","status":"publish","type":"page","link":"https:\/\/3cxcloud.lt\/en\/history-of-telephony\/","title":{"rendered":"The history of telephony"},"content":{"rendered":"\t\t
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HISTORY OF TELEPHONY<\/h1>

From the first call in 1876 to cloud telephony<\/p>

How the telephone went from a wired set to a cloud service: the key dates, the generations of the company phone system, the mobile phone generation by generation, and the terms that keep coming up in modern telephony.<\/p>

Book a demo<\/a>3CX Cloud LT solutions<\/a><\/div><\/div>
<\/linearGradient><\/defs>1876 \u2192 TODAY<\/text>1876<\/text>1915<\/text>1962<\/text>1983<\/text>1995<\/text>WIRED LINE<\/text><\/g><\/g>CLOUD TELEPHONY<\/text><\/svg><\/div><\/div><\/section><\/div>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/section>\n\t\t\t\t
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In 1870 two inventors, Elisha Gray and Alexander Graham Bell, were independently designing a device that could carry human speech electrically \u2014 the telephone. Both were racing, but A. G. Bell patented his first.<\/h2>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/section>\n\t\t\t\t
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\u201cMr Watson, come here. I want to see you.\u201d \u2014 the first words ever spoken on a telephone, said by A. G. Bell to his assistant on 10 March 1876, calling into the next room.<\/b><\/h3>

The telephone came out of attempts to improve the telegraph. The telegraph was essentially just a faster way of sending letters and messages, and it was while trying to improve it that Bell had the idea of a \u201ctalking\u201d telegraph \u2014 a way to carry a voice down a wire and let people speak across a distance.<\/p>

The switching system, signal amplifiers and call multiplexing used in telegraphy were adapted, and telephony had a path to develop along.<\/p>

The first telephone users were mostly businessmen, because only they could afford a fairly expensive service. In the early twentieth century a row of black telephones stood on the desks of textile magnates and railway barons \u2014 one telephone per line. In the mid-1920s the Bell System came up with something better: instead of a row of telephones on the desk, it connected a row of lines to a single instrument. That freed up the desk and made work simpler.<\/p>

\"Telephony\"<\/p>

The switchboard spread through the 1880s and, as the system grew exponentially, call switching had to be automated. At first there was no dialling system, no electronic switches and no signalling. The caller turned a crank, and the current it generated signalled the operator. To connect the subscriber, the operator plugged cords into the right line. For a long-distance call the operator had to reach another operator on an external line, then perhaps another, and so on until the right subscriber was reached.<\/p>

As call volumes grew, serving them all took a great many operators, which became expensive and unreliable, demanded a lot of space and certain working conditions. That way of connecting also became too slow. As early as 1889 A. B. Strowger of Kansas City devised an automatic dial switch \u2014 dial calling, where a call is routed through a system of switches using pulse signals \u2014 which needed no operator at the exchange. In 1921 the first fully automatic switching system went into service in Omaha, USA. Over time both central exchanges and company PBXs were automated. Direct long-distance dialling took longer to arrive. The first computerised switch entered service in 1976, and by 1982 half of all calls were connected electronically.<\/p>

Over the following fifty years company PBXs grew more capable and gained extra functions: hold buttons, indicators, paging, mute, music on hold, long-distance call barring, timers and memory. Many competing companies built these systems. One drawback of \u201celectromechanical\u201d switching remained throughout: a great deal of cabling.<\/p>

A clash of technologies was coming. Convenient switched telephones saved money, because an expensive operator was no longer needed, but they were hard to install, maintain and repair with their heavy cables.<\/p>

\"\"<\/div>

A solution was found \u2014 a technical one. In the late 1970s several innovative companies built electronic switching systems in which a thin cable with four to eight copper strands replaced tens or hundreds. That made installation far easier, cheaper and more reliable. Advances in microelectronics arriving at the same time made previously expensive features \u2014 speakerphones, message recording \u2014 available for a small extra cost.<\/p>

As the number of subscribers grew, the technology matured and the whole telephone system expanded, both call prices and connection times fell. That trend has continued, and international calls now cost a small fraction of what they once did.<\/p>

Until the twentieth century, telephone systems used twisted copper pairs. In 1927 radio relay links made it possible to connect the USA and Great Britain. Another important step was coaxial cable, which arrived in 1940. It lowered noise and raised capacity \u2014 vital for an ever-expanding telephone network.<\/p>

Microwave stations in the 1950s, built on radar technology, could carry around 20,000 telephone conversations. Communication satellites for trunk links appeared in 1965.<\/p>

Digital transmission arrived in 1962. In the old analogue system the electrical signal travelling down the wire essentially reproduced the sound waves in the air. In a digital system what travels down the wire is information about the sound wave, not an image of it.<\/p>

Because optical cable and optical technology were expensive, work began on how existing telephone lines could be used, and integrated services digital networks were developed.<\/p>

Telephony from then to now<\/b><\/h3>

Telephony has moved remarkably fast in recent decades, from wired analogue systems to digital, wireless and internet-based ones.<\/p>

Mobile networks: from 2G to 5G, and 6G ahead<\/b><\/h3>

2G (1991) \u2014 the first digital mobile technology, which brought SMS and better call quality.
3G (2001) \u2014 made web browsing, email and video calling possible.
4G (2009) \u2014 mobile internet became fast enough for video streaming and high-quality VoIP calls.
5G (2020) \u2014 cut latency sharply, raised data rates and made it possible to control IoT devices, smart cities and autonomous vehicles in real time.<\/p>

\"5g<\/p>

Every step in this history brought real change. 5G, for instance, moves data almost instantly, which opened possibilities in everyday life and in business alike: it cut latency significantly and made connections more dependable. It also opened the way to autonomous vehicles, the internet of things and smart cities \u2014 advances with enormous potential to transform whole industries.<\/p>

6G, expected after 2030, should bring higher speeds again (above 1 Tbps), real-time artificial intelligence and more advanced holographic communication.<\/p>

<\/p>

VoIP <\/a>and cloud telephony<\/b><\/h3>

\"\"\"\"<\/p>

Internet-based phone systems such as 3CX Cloud LT<\/a>, Zoom, Microsoft Teams, WhatsApp and Skype have displaced traditional fixed-line calling. Cloud computing let businesses run virtual call centres with no physical infrastructure, cutting cost and adding flexibility.<\/p>

Artificial intelligence and automation<\/b><\/h3>

Voice recognition and chatbots \u2014 AI helps automate customer service and lets call centres handle enquiries more efficiently.
Predictive analysis \u2014 businesses can analyse call data and anticipate what customers will need.
Smart assistants \u2014 Google Assistant, Alexa and Siri can place orders by phone, book restaurant tables and control smart home devices.<\/p>

Optical and quantum links<\/b><\/h3>

Optical cable carries large volumes of data with almost no delay.
Quantum communication, still ahead of us, promises highly secure encrypted links that cannot be intercepted.<\/p>

How the smartphone evolved<\/b><\/h3>

Phones became not only a means of communication but personal computers, cameras, payment tools and health monitors. Folding screens, haptic feedback and virtual or mixed reality are steadily becoming everyday features.<\/p>

Where telephony is heading<\/b><\/h3>

Deeper AI integration \u2014 phones will act more autonomously, understanding what the user needs and making decisions.
Traditional telephony matters less \u2014 physical phone networks are becoming obsolete, replaced by internet communication.
Security matters more \u2014 encrypting calls and data will become even more important, especially in the era of quantum technology.<\/p>

Connected digital ecosystems \u2014 phones, computers, smart devices and cars will be linked ever more closely, for one seamless experience.<\/p>

Read more<\/a><\/i><\/b><\/p>

Over the past 150 years telephony has been transformed \u2014 from A. G. Bell’s first words to AI-driven conversations and experiments in quantum communication. It will keep getting faster, safer and more closely woven into daily life.<\/b><\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/section>\n\t\t\t\t

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How the handset changed<\/span>

Mobile phone generations<\/h2>

In half a century the telephone went from a prototype weighing about a kilogram to a device that holds every work conversation. Each generation changed not only the size, but what a phone can actually do.<\/p>

  1. <\/svg><\/span>1973<\/span>First handheld<\/b>A prototype weighing about a kilogram. Long antenna, no display \u2014 calls only.<\/span><\/li>
  2. <\/svg><\/span>1983<\/span>The commercial \u201cbrick\u201d<\/b>The first phone you could buy: a single-line display and a full keypad.<\/span><\/li>
  3. <\/svg><\/span>1992<\/span>First GSM<\/b>A digital network brings SMS, and the handset fits into a bag.<\/span><\/li>
  4. <\/svg><\/span>1996<\/span>Clamshell<\/b>The screen hides under a lid \u2014 the phone fits in your palm.<\/span><\/li>
  5. <\/svg><\/span>2003<\/span>Colour screen<\/b>A camera and colour arrive: the phone is no longer just for talking.<\/span><\/li>
  6. <\/svg><\/span>2007<\/span>Touchscreen<\/b>The keypad disappears and the screen takes over the whole front.<\/span><\/li>
  7. <\/svg><\/span>2020<\/span>Full-screen smartphone<\/b>5G, several cameras and the apps where work conversations now happen.<\/span><\/li><\/ol><\/section>
    Timeline<\/span>

    Key dates in telephony<\/h2>

    The road from the first patent to today\u2019s networks, split into five periods. Only the dates that changed the principle of communication are included, not those that merely improved it.<\/p>

    Every date can be expanded to see what exactly was built.<\/p>

    1876\u20131891<\/span>The beginning<\/h3>
    1. 1876<\/span>The telephone patent.<\/b> Alexander Graham Bell patents the telephone. On 10 March he calls his assistant in the next room.
      How it worked<\/summary>

      In Bell's device sound becomes a varying electric current. As you speak, a diaphragm vibrates and a needle attached to it dips deeper or shallower into acidified water \u2014 the resistance of the circuit changes, and so does the current. At the far end an electromagnet uses that same current to move a membrane, and the sound is reproduced. There is no amplifier yet, so you can talk only as far as the resistance of the wire allows.<\/p><\/details><\/span><\/li>

    2. 1878<\/span>The first telephone exchange.<\/b> The first commercial telephone exchange opens in New Haven (USA) \u2014 21 subscribers.
      How it worked<\/summary>

      Every subscriber runs their own pair of wires to the exchange. There stands a manual switchboard: the operator sees a calling indicator, asks who to connect, and joins two pairs of jacks with a patch cord. The subscriber calls the exchange by turning a hand generator that sends the ringing current.<\/p><\/details><\/span><\/li>

    3. 1891<\/span>The automatic switch.<\/b> Almon Strowger patents the automatic switch. Connecting a call no longer needs an operator.
      How it worked<\/summary>

      While dialling, the disc interrupts the line current: the digit 5 means five pulses. In the exchange those pulses drive a step-by-step selector: the first digit lifts the contact brush to the right level, the second rotates it to the right contact. Connecting becomes the work of a mechanism, so the operator is no longer needed.<\/p><\/details><\/span><\/li><\/ol><\/div>

      1915\u20131956<\/span>The network expands<\/h3>
      1. 1915<\/span>A call across the continent.<\/b> The first conversation from New York to San Francisco \u2014 the telephone crosses a continent.
        How it worked<\/summary>

        A five-thousand-kilometre line only works if the signal is restored along the way. The vacuum tube (triode) made that possible: amplifiers installed along the route lifted the weakened signal. Loading coils were used as well, reducing attenuation in the cable itself.<\/p><\/details><\/span><\/li>

      2. 1921<\/span>A fully automatic exchange.<\/b> The first fully automatic switching system starts working in Omaha (USA).
        How it worked<\/summary>

        In Omaha the whole city network, not a single line, was switched over to automatic Strowger-type equipment: subscribers dialled local calls themselves, and operators were left only for long distance.<\/p><\/details><\/span><\/li>

      3. 1927<\/span>Radio link across the Atlantic.<\/b> Radio relay lines connect the USA and Great Britain.
        How it worked<\/summary>

        Voice crossed the ocean by long-wave radio \u2014 a cable able to carry a conversation did not exist yet. There was a single channel, dependent on weather and the ionosphere, and to keep outsiders from listening the frequency band was inverted.<\/p><\/details><\/span><\/li>

      4. 1940<\/span>Coaxial cable.<\/b> Less noise and more capacity \u2014 a necessity for the growing network.
        How it worked<\/summary>

        The signal travels not between two parallel wires but between an inner conductor and the shield around it. The shield keeps interference out, so much higher frequencies can be used. Each conversation gets its own carrier frequency (frequency-division multiplexing), and hundreds of calls travel along one cable.<\/p><\/details><\/span><\/li>

      5. 1956<\/span>The TAT-1 cable.<\/b> The first transatlantic telephone cable, with 36 speech channels.
        How it worked<\/summary>

        Two coaxial cables were laid \u2014 one for each direction \u2014 with submerged vacuum-tube repeaters along them that had to run for decades without service. Frequency-division multiplexing produced 36 voice channels; until then voice crossed the ocean by radio only.<\/p><\/details><\/span><\/li><\/ol><\/div>

        1962\u20131976<\/span>Going digital<\/h3>
        1. 1962<\/span>Digital transmission.<\/b> The wire no longer carries an image of the sound wave but information about it. The same year \u201cTelstar 1\u201d begins relaying calls from space.
          How it worked<\/summary>

          Sound is measured 8,000 times per second and each measurement is written in eight bits \u2014 one conversation becomes a 64 kbit\/s stream (PCM). Time-division multiplexing puts a few dozen such streams on one line, and repeaters no longer amplify the signal \u2014 they rebuild the pulses from scratch, so noise stops accumulating. That same year Telstar 1 received on one frequency and retransmitted on another.<\/p><\/details><\/span><\/li>

        2. 1963<\/span>Tone dialling.<\/b> DTMF (tone) dialling replaces the rotary dial \u2014 a number is entered several times faster.
          How it worked<\/summary>

          Each key sends two audio tones at once \u2014 one from the low group, one from the high. Such a combination does not occur naturally in speech, so the exchange recognises it without confusion. Most importantly, the tones travel on the same channel as the voice: a number can be dialled after the call is already connected \u2014 and from that voice menus later grew.<\/p><\/details><\/span><\/li>

        3. 1973<\/span>The first mobile call.<\/b> Martin Cooper (\u201cMotorola\u201d) makes a call on a handheld mobile phone.
          How it worked<\/summary>

          The prototype weighs about a kilogram because of the battery: the transmitter needs a lot of power, since the link is analogue and each conversation gets its own radio frequency. The call holds as long as the handset stays within one base station's area \u2014 handover between stations does not exist yet.<\/p><\/details><\/span><\/li>

        4. 1976<\/span>A computerised switch.<\/b> Calls start being connected by software rather than electromechanics.
          How it worked<\/summary>

          Switching logic moves out of relays and wires into a program: the exchange has a processor and memory, and the path of a call is decided in software. At the same time what is switched is already a digital stream \u2014 a time slot rather than a line. New features (forwarding, hold, transfer) become a change of program, not a purchase of new equipment.<\/p><\/details><\/span><\/li><\/ol><\/div>

          1983\u20131991<\/span>Mobile networks<\/h3>
          1. 1983<\/span>The first cellular network.<\/b> The first commercial cellular (1G) network starts operating in the USA.
            How it worked<\/summary>

            The territory is divided into cells, each with its own base station and its own set of frequencies. The same frequencies are reused in non-adjacent cells, so network capacity no longer depends solely on how many frequencies there are. While moving, the call is handed from one cell to the next, so you can talk while driving.<\/p><\/details><\/span><\/li>

          2. 1991<\/span>GSM (2G).<\/b> The first digital mobile network launches in Finland \u2014 SMS appears.
            How it worked<\/summary>

            Voice is digitised and compressed by a codec down to about 13 kbit\/s. One 200 kHz frequency channel holds eight conversations \u2014 each gets its own time slot. The radio link is encrypted, and the subscriber is separated from the handset by a SIM card. SMS travels on the signalling channel \u2014 which is why it fits only 160 characters.<\/p><\/details><\/span><\/li><\/ol><\/div>

            1995\u20132019<\/span>Internet and cloud<\/h3>
            1. 1995<\/span>The first VoIP application.<\/b> \u201cVocalTec Internet Phone\u201d makes it possible to talk over the internet, bypassing the phone line.
              How it worked<\/summary>

              Sound from the microphone is digitised, compressed and packed into IP packets that travel the internet like any other data. No telephone line is needed, but there are no quality guarantees either: packets are delayed or lost. The same program has to run at both ends.<\/p><\/details><\/span><\/li>

            2. 2002<\/span>The SIP standard.<\/b> SIP (RFC 3261) is approved \u2014 the protocol IP telephony still runs on today.
              How it worked<\/summary>

              SIP is a text protocol, similar to the browser's HTTP: it only sets up, modifies and ends a call, while the sound itself travels separately. A subscriber is addressed by name rather than by wire, and a registration server knows which device they are currently reachable on. That is why equipment from different vendors finally talks to each other.<\/p><\/details><\/span><\/li>

            3. 2009<\/span>4G LTE.<\/b> The first commercial 4G networks start operating in Stockholm and Oslo.
              How it worked<\/summary>

              There is no separate voice channel left in the network \u2014 everything, calls included, travels as IP packets. The radio interface uses several antennas at once, and latency drops to tens of milliseconds. That is exactly what made voice and video calls on mobile as smooth as on a fixed line.<\/p><\/details><\/span><\/li>

            4. 2011<\/span>WebRTC.<\/b> Voice and video calls straight in the browser, without a separate application.
              How it worked<\/summary>

              Everything a call needs is built into the browser: access to microphone and camera, audio and video codecs, encryption and a way through the router. All that is left is agreeing how the two parties will find each other \u2014 that is done separately, often with the same SIP. No software has to be installed.<\/p><\/details><\/span><\/li>

            5. 2019<\/span>5G.<\/b> The first commercial 5G networks (South Korea); more widely in Europe from 2020.
              How it worked<\/summary>

              The new radio interface uses wider frequency bands, multi-element antenna arrays and beamforming \u2014 the signal is sent towards the device rather than in all directions. The network can be divided into logical slices, each guaranteed its own speed and latency.<\/p><\/details><\/span><\/li><\/ol><\/div><\/section>

              The company phone system<\/span>

              How did the phone system end up in the cloud?<\/h2>

              Over a century the company phone system went through four generations. All of them solved the same task \u2014 connecting a call to the right person \u2014 just depending less and less on cables and hardware.<\/p>

              1. Analogue PBX<\/b>Every handset had its own pair of wires running to the exchange, and the features were built into the hardware itself. Changing anything meant changing equipment.<\/span>
                How it worked<\/summary>

                Every internal phone has its own copper pair to the exchange, and the features are built into cards: as many cards, as many possibilities. A call is switched physically \u2014 wire joined to wire. A new employee means a new line from the exchange to the desk.<\/p><\/details><\/li>

              2. Digital PBX<\/b>Electronic switching and a thin cable instead of dozens of wires. Voicemail, call queues, music on hold and call transfer appear.<\/span>
                How it worked<\/summary>

                Inside the exchange voice is already digital, and what is switched is a time slot rather than a line. One cable carries both the conversation and the signalling to the phone, so the phone can have a display and feature keys. Voicemail, queues, music on hold and transfer become part of the exchange software.<\/p><\/details><\/li>

              3. IP telephony (IP-PBX)<\/b>The call travels over the same network as the data, and the SIP standard lets equipment from different manufacturers talk to each other. A separate telephony cable network is no longer needed.<\/span>
                How it worked<\/summary>

                The call is packed into IP packets and travels the same computer network as files or email. The phone plugs into an ordinary network socket, and the SIP standard lets phones and exchanges from different vendors talk to each other. The link to the operator runs over a SIP trunk, so the number of channels can be changed without changing equipment.<\/p><\/details><\/li>

              4. Cloud telephony<\/b>The phone system is no longer a box in the server room. Numbers, queues, recordings and reports are managed in a browser, and staff connect from the office, from home or from a phone.<\/span>
                How it worked<\/summary>

                The exchange software runs in the provider's infrastructure, and all that reaches the company is an internet connection. A desk phone, a computer application or a browser registers with that exchange from anywhere, so the workplace is no longer tied to a building. Updates, backups and resilience stay on the provider's side.<\/p><\/details><\/li><\/ol>

                Moving over does not mean replacing everything at once: upgrading an old phone system<\/a> happens in stages, and the numbers and extensions stay the same.<\/p><\/section>

                Glossary<\/span>

                What do the telephony terms mean?<\/h2>

                A few abbreviations keep coming up when reading about the history of telephony. Here is what they mean.<\/p>

                PBX (phone system)<\/dt>
                A company phone system that connects internal handsets to each other and to the outside network. It is what decides who answers when a customer calls.<\/dd><\/div>
                VoIP<\/dt>
                Carrying voice over an IP network instead of a separate phone line. The term covers both calls over the internet and the company\u2019s internal network.<\/dd><\/div>
                SIP<\/dt>
                The protocol that sets up, manages and ends a call. Since 2002 it has been the main IP telephony standard.<\/dd><\/div>
                SIP trunk<\/dt>
                A digital link between the phone system and the operator that replaced physical lines. The number of channels can be changed without changing equipment. More \u2014 SIP connections<\/a>.<\/dd><\/div>
                DID (direct number)<\/dt>
                An external number that rings straight to a specific employee\u2019s handset, without going through reception.<\/dd><\/div>
                IVR (voice menu)<\/dt>
                An automated attendant with options (\u201cpress 1\u201d) that routes the call to the right department.<\/dd><\/div>
                WebRTC<\/dt>
                A technology that lets you talk and see video straight in the browser, without a separate application.<\/dd><\/div>
                Cloud telephony<\/dt>
                The phone system runs on the provider\u2019s infrastructure and the company uses it as a service. No server of your own, no maintenance, no updates.<\/dd><\/div><\/dl><\/section>
                Today<\/span>

                Where does the history of telephony continue today?<\/h2>

                The same tasks \u2014 answer the call, do not lose the customer and know what was said \u2014 are solved today by software, not by cables.<\/p>