Historic Voice World

Before we go into to CCNA voice series, we need to take a step back in the history and look at the historic voice world. The reason why we are going here is that the historic voice world will be around for many years to come. The truth is that there are still millions of people using rotary phones, so the world does not always moves as fast as we want it to. 

The idea behind understanding historic voice world is to know how to integrate the historic voice world with VoIP. And to do that we need to have the base understanding, we will not talk about Alexander Graham Bell’s theories and like that, rather we will focus how analog voice does work and what is the take to get that over VoIP world. So we will talk about historic voice world starting with analog connections, what it means to have an analog connection. 

Then we will talk about electric waveforms more than you ever new. From there we will go for understanding of analog signaling itself. It will dive more into exactly what we need to configure on over Cisco routers to interface with that environment. Late 1800 and early 1900 was amazing time to live in. it was a time when inventions and new technology was coming out daily. Thomas Edison in 1877 invented phonograph. 

 

It was a device that could store signals by using a cylinder covered in tin foil. Sound was collected by a horn, which caused a diaphragm to vibrate. This was connected to a needle, so when the diaphragm vibrated (because of the sounds) - indents or grooves were made on the tin foil. This "stored" the sound. In order to playback the sound - the needle go over the grooves, causing the diaphragm to vibrate in the same way it had before. These vibrations reproduce the original sound.

When Thomas created that phonograph in 1877, decided that making dense in the tin foil (density is the property of media) is what is stored and relayed to generate voice. As the technology progressed the tin foil phonograph were replaced by magnetic tapes whose magnetic field is used to store and regenerate voice. Record players use this mechanism.

 

Braille for the blinds is a way of analog transmission as it makes the paper dense and the people who are blind gets the information from these dense areas. So here we can give a very basic definition of analog transmission as

“The transmission method that uses the property of the transmission media (such as continuous signals) to convey information (from modem to modem) is called analog transmission”.  

Similarly our home phone lines use electricity (which is the property of phone line and continuous in nature) for voice transmission, so our phone lines provide us analog connectivity.  

When we have analog connectivity then analog transmission methods are used. According to Wikipedia

“Analog (or analogue) transmission is a transmission method of conveying voice, data, image, signal or video information (from modem to modem) using a continuous signal (as carrier) which varies in amplitude, phase, or frequency”.

Analog transmission is the transfer of analog source signal, using an analog modulation method such as Frequency modulation (FM) or Amplitude modulation (AM), or no modulation at all. 

Data transmission, digital transmission, or digital communications is the physical transfer of data (not a method of conveying information from modem to modem). Data is transmitted as a bit stream in the form of voltage pulses over a point-to-point or point-to-multipoint communication channel such as copper wire (twisted pair cable), optical fibers etc. Our LANs provide digital connectivity.