The Evolution of Telephony

Lazaros Agapidis

Oct 19 2020

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Today, a multitude of businesses and professionals are familiar with Voice over IP and IP telephony technologies.  Many of their benefits have been experienced firsthand, and countless businesses have benefitted from the flexibility and versatility these technologies deliver.

But how did we get here?  What aspects of today’s communication technologies actually come from traditional telephony, and what part did these older technologies play to get us to where we are currently?  In this article, we’ll take a look at the roots of VoIP and its evolution as it developed into what we see today.

Traditional telephony technologies

When we speak about traditional, or conventional telephony, we are referring to all the technologies that made telephone services possible before the advent of VoIP.  Until the late 1990s when VoIP was still in its infancy, all telephony services worldwide were based on analog lines, digital ISDN circuits, and conventional PBXs.

But the services, how they functioned and even the level of quality and reliability that traditional telephony delivers played a vital role in the evolution and development of VoIP.  If you’ve used VoIP services, you yourself can verify this simply by comparing your experience with the descriptions below, giving you an opportunity to understand why many aspects of today’s VoIP services function the way they do.

Keeping things the same

VoIP has left many of the mechanisms and procedures used by traditional telephony unchanged, causing the general feel of using a telephone, VoIP or otherwise, to remain the same.  This is done in order to facilitate the adoption of the new technology by users, and to eliminate any kind of learning curve for the fundamental service provided.  Some of the most common aspects that have remained the same are further described below.


Telephone services use a series of tones with particular meanings that are used to convey to the user what the status of the call is.  Dial tone, ring back tone, and the busy tone are just some of those that have been adopted by VoIP.  Tones involved in processes such as call waiting, leaving a voicemail, as well as the reorder tone have remained the same for decades.  VoIP has purposefully incorporated these as part of its fundamental operation for the purpose of user familiarity, as well as for the easy interoperation with more traditional telephony networks.

Dial pad

The Dual Tone Multi Frequency (DTMF) keypad, more colloquially referred to as the touch tone keypad, was introduced in the 1960s.  The tones produced by these keypads were used to actually signal and instruct telephony equipment.  According to AT&T, the inventor of the technology, the touch tone keypad is used as “a method for pushbutton signaling from customer stations using the voice transmission path.”  In today’s VoIP systems, these audible tones no longer have any meaning, since signaling is taken care of by protocols such as the Session Initiation Protocol (SIP).  However, these tones can still be heard by users when dialed, simply for familiarity’s sake.


Many of the features delivered today by VoIP services have their roots in the traditional telephony era.  Call hold, call transfer, call waiting, call park, call conferencing, and many other features were introduced as options available to both standalone business lines as well as to internal extensions of a business PBX.  All of these features, which originated before VoIP itself, have been adopted into VoIP systems and have been engineered to function in exactly the same way as their traditional counterparts.  The actual procedures used, the buttons pressed to engage these features, have remained unchanged, once again, to eliminate the need for training and learning new processes.

Voice quality

Anyone who has used any type of telephone will immediately recognize the characteristic timbre, or quality that a voice acquires when heard over the phone.  The human voice, like any sound, is a result of sound waves vibrating at varying frequencies through the air.  Specifically, the typical human voice spans a range from about 125Hz to 8000Hz.  When we speak, multiple frequencies and their harmonics combine to produce what we hear.

Now when the first telephones transmitted voice over a cable in the form of electrical signals, they limited the range of frequencies that could be transmitted to between 300Hz and 3400Hz.  This range was chosen because these are the most used frequencies of the human voice during normal speech.  Even so, this limitation creates the telephone-sounding timbre we are so familiar with.  This limitation is even more pronounced if you attempt to listen to music over the phone, whose frequencies range from 20Hz to 20000Hz.  You will find that the quality of music is drastically reduced.

Now this same principle was implemented when analog telephone lines were converted to digital ISDN lines and when those in turn were converted to the use of VoIP.  Digitization of voice uses a process of sampling, which when applied at the proper rate, confines the frequencies of voice to within the aforementioned frequency range, resulting in exactly the same sound quality.  This sound quality is often referred to as toll quality voice, a remnant of traditional telephony terminology.


Of course, traditional telephony has its limitations, otherwise there would be no need for a newer technology to replace it.  Some of the most fundamental limitations include:

  • Location specific – A telephone line must be used at the physical location, i.e. the building, at which the telephone circuit terminates.
  • Limited interaction – Traditional telephony doesn’t easily interact with other applications
  • Lack of flexibility – The implementation of multi-site telephone systems, the accommodation of mobile employees, and the inability to provide customized service packages are all limitations that have been overcome using VoIP.

Evolution of VoIP beyond conventional telephony

Even though many of VoIP’s characteristics stem from similarities found in conventional telephony, VoIP technologies have not been implemented simply to emulate what traditional telephony can achieve.  It is bound to go above and beyond anything that traditional telephony could have been imagined to be.


Arguably the greatest leap that VoIP has taken beyond conventional telephony is its ability to offer services that are not tied down to a physical location.  You can enjoy advanced VoIP services anywhere Internet connectivity is available, whether wired or wireless.  This fact has enabled employee mobility and remote working to a degree never before seen or conceived.  Services such as OomaOffice offer you the ability to terminate a particular phone number on your smartphone app, your desktop, or a physical IP phone on your desk, regardless of where these devices exist physically.


VoIP services are no longer limited simply to transmitting voice, but enrich communication by including high-quality video, shared virtual workspaces, messaging, and many other collaboration tools.  Voice is no longer limited to toll quality, but can take advantage of wideband codecs transmitting CD quality sound.  GoToConnect is an excellent example of a provider that delivers such high-quality collaboration services as complete packages for their customers.


Traditional telephony technicians could not even dream of a time when telephony would be delivered to businesses as a service that requires no on-site equipment beyond Internet connectivity.  RingCentral is an example of a service where all infrastructure is kept in “the cloud” and customers need only a smartphone or desktop application to use its services.

Interconnection with other services

One of the most innovative and future-facing aspects of VoIP is its ability to be interconnected with other services including CRMs, helpdesk applications, productivity suites, and third-party collaboration systems, to name a few.  Such integration vastly increases productivity and efficiency and provides specialized services especially in contact center environments.


It’s easy to forget that traditional telephony, since it started to be widely deployed in the United States in the 1930s, had over seven decades to mature.  By the late 1990s, its natural technological limitations were reached.  Since then, for the past twenty years, VoIP has continued to grow in both usage and technological advancement, and where it will lead in the future can only be speculated.

VoIP’s evolution is expected to proceed much more quickly than that of conventional telephony, and if that is the case, we have much to look forward to in the near and not so near future.

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