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Switches in BSNL:

 

I have attended BSNL in-plant in which I came to know some of the switches.

 

For Local Calls:

 

In Olden days, when you pickup the hand set, a person picks up and asks for the number you want to connect with. After you give the number, the person connects your extension to the person you wish to talk with. Then his/her phone will ring, after the person picks up, connection will be established.

 

Then Mechanical switches came into picture. As you dial the number, the switch analyze the number and connects  automatically.

 

Now digital switches are used in BSNL which is called OSS switch. C-DOT manufactures the switch

 

C-Dot switchC-Dot switch

 

 

 

 

 

 

 

For Trunk Calls:

 

In Olden days, STD calls takes 10 hours to connect. When you pickup the handset, agent asks for the number you wish to talk to. Then he asks to wait. After Trunk connection is established, your phone and other person's phone will ring. When both picks up the call, connection is established. For Eg: you pickup the handset at 10:00 am and informed the exchange the number you wish to connect to, he will ask to drop the call and wait. Exchange guy will initiate the trunk connection. Your  local exchange and recipient's local station will be connected to trunk. Then the person in the exchange near to recipient will connect to his phone. When connection is established, both your phone and recipient's phone will ring. When the recipient attend, the exchange guy will inform that you have initiated the connection, when you pickup the headset, exchange  guy will inform that you have initiated the call at 10:00 AM and it is now connected. Then you and your friend will be connected. When you initiate the call, depending on state which you are calling to and distance, connection timing will vary.

 

Imagine you are in TamilNadu and wants to make a call to Rajasthan, if you initiate the call at

10:00 AM, the call will be connected at 8:00 PM!!!. Then BSNL introduced different speeds. Based on the speed you select, the charges apply. Thanks to technology, you will get connected in seconds.

 

In Olden days, STD calls will be charged at 32 Rupees per minute/30 secs/15 secs/10 secs based on distance. Thanks to Jio. You provide at virtually zero cost.

 

Trunk line used in Olden daysTrunk line used in Olden days

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Trunk LineTrunk Line

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Now it is replaced by Optical Fiber. You can see BSNL OFC boards.

 

OFC used these days instead of wires to connect STD callsOFC used these days instead of wires to connect STD calls

 

 

 

BSNL now uses Next Generation Network. In which, all Trunk switches will be assigned IP address.

 

For ISD Calls:

 

Telecom networks uses undersea optical cables for International call and internet routing.

 

In Olden days, ISD calls will be charged Rs.64 for per minute/30 secs/15 secs/10 secs based on distance.

 

International cables used are SEA-ME-WE 3, SEA-MEA-WE-4 (Backup), I-ME-WE etc.

 

Kindly refer https://www.submarinecablemap.com/

 

 Parts of Undersea CableParts of Undersea Cable

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Ship laying Undersea cableShip laying Undersea cable

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Undersea Cable RepairUndersea Cable Repair

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Maths  used in Calculation. You can see differentiation here. X with respect to T. Differentiation is applied hereMaths used in Calculation. You can see differentiation here. X with respect to T. Differentiation is applied here