INTRODUCTION TO TELECOM

Invention of Telephone

Graham Bell invented telephone in the year 1876.
The first call was successfully made between Graham Bell and president of USA Raymond B hayes.

Dialing in Telephony

1) Analog Dialing
2) Pulse Dialing
3) DTMF (Dual Tone Multifrequency

Analog Dialling

It is nothing but rotary dialling which was the first one used in landlines.

Takes long time for dialling, but the reliable one.











Pulse Dialling

It takes same time as analog dialling but just keypad is in different type.
Pulses are generated in single touch instead of rotating.
i.e

If pressed one time : One pulse is generated
If pressed two times : Two pulses are generated
If pressed three times : Three pulse are generated
If pressed four times : Four pulses are generated as shown in below diagram

Disadvantages
1) Takes long time for dialling.
2) chance of connecting wrong numbers is possible.


Dual Tone Multi Frequency

Advantages:-
1) Takes very short time for dialling
2) No chance for wrong numbers

Now a days only DTMF is used in Telephony.