VoIP vs ISDN

Introduction

In the early 1980s, the marketers of compact disks began testimony that all digital media were superior to their analog counterparts.  While this was untrue with many early CDs, it did seem clear to the market that digital was the wave of the future, and this was true.  Thus did all become digital.  Digital turntables and speakers, digital alarm clocks, and coffeepots (perhaps this was the inspiration for Apple’s digital toasters, but archaeologists are unsure).

Voice over Internet Protocol (VoIP) must therefore be superiorist of all.  That may follow from this choppy logic but it is untrue.  Our job here is to find and share what is true in modern telecommunications.

Voice

After Bell’s first call got him help from Watson, telephony began its refinement.  Among the first issues addressed was voice recognition, and experimenters determined that each human voice is uniquely recognizable (in range and harmonics) if given bandwidth of 2,500 cycles per second (2.5 kiloHertz).  That standard is still in effect today for simple voice transmission, regardless of medium, format or protocol.  We recognize it instantly. 

Digital Voice

Analog telephony flourished because: 

• The technology is simple.
• People want to communicate
• After initial investment in plant and equipment, it is enormously profitable for its owners.

The success of the telephone industry eventually caused its problems:  Too many users making too many calls for the analog technology to handle.  The Bell System responded to the challenge, first by developing Information Theory and its practical applications at Bell Labs.  Western Electric followed by engineering the equipment that exploited the advantages of this research.  AT&T and the old Bell Operating Companies deployed the technology into the field. 

We have related this history earlier on this website.  Its principal importance here is to underline that digitization of voice has been common practice for more than forty years.  Further, bandwidth (2.5 kHz) used by a caller and received by a listener has not changed.  Your friend’s voice (which eventually, is always analog) on the phone sounds the same regardless of whatever the intervening technology may be.  Unless that technology screws it up.