how telephones work

Rather than telling you how telephones work in detail this article is going to give you an overview of how telephones work.  An in depth explanation of how telephones work can be found in your home library or through on-line encyclopaedias.

So how telephones work? – Analogue:  Normally over two wires (Tip and Ring) with 48 volts dc supplied from the local exchange.  Why 48V?  So that distant telephones have sufficient voltage to work.  Speech is superimposed on the line and extracted by resistor, capacitor and inductor networks in the phone and presented to the earpiece.  The microphone picks up your words and injects them through similar circuitry.

How telephones work? – Digital TDM:  In this technology the analogue signals are converted by an A-D converter into a digit code of noughts and ones to represent the audio signal.  This is transmitted in a specific time slot enabling multiple conversations to pass along the same cable.  Switching is more effective as it can be achieved digitally instead of though a matrix of contacts.  This is the communications means of ISDN.

How telephones work? – IP:  It is analogous to the previous section but rather than only using a dedicated voice network, the digits are packaged in the same way as data and transferred between ip-addresses.  It also works over wireless frequencies.

As space is short here to tell you how telephones work why not ring TelephoneSystemsDirect on 0800 652 8052  to learn more?