Alternate Communication systems during disasters Chapter Notes - Class 10 PDF Download

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Introduction
A well established communication system is very essential during a disaster. People have to be informed of impending disasters and they have to be given instructions to meet the disaster with least casualty.

Rescue and relief operations depend a great deal on an efficient communication system.
Rescue teams have to know were relief materials are available and they need to know the particular requirement of the area. They should also know of any further disaster in that area and most of all there should be coordination among the members of the team, to make the rescue operation successful.

For all this an effective and reliable communication system is necessary.

The Public wired telephone, known as the Public Switched Telephone Network – PSTN – is the most popular means of communication today.

The PSTN connects all government and private offices, police stations, fire stations, hospitals and a majority of homes and business places by transmitting and receiving voices, fax and data.

The wireless telephone or the mobile telephones are becoming very popular today because of its versatility. It came be carried anywhere and it is compact.
The satellite is used for wireless communication.

Disruption of Telecommunication Networks During Disasters
Normal telecommunication networks usually get disrupted or jammed during a disaster.
Earthquakes, cyclones, floods and landslides severely damage the infrastructure of the network.

Cables or the transmitting towers are damaged or the power supply is disrupted during a disaster. When this happens the telephone fails to function. Even the wireless telephones get disrupted as they also depend on the transmitting towers.

During a disaster, as many people want to use the telephone line to that particular area , the cables get jammed and the communication system fails to work. 

As there is a possibility of the existing communication system to fail during a disaster, it is very important to have an alternate system of communication that can be used during disasters, as we know communication is very important during a disaster.

Communication Networks of the Government of India
There are two major networks run by the government of India. They are:
(i) NIC – National Informatics centre
(ii) BSNL – Barath Sanchar Nigam limited

(i) NIC-National Informatics Centre:-
NIC is a premier Science and Technology organization of the Government of India. It functions through a nation wide information and communication technology network called NICNET. The Secretariats of all the States and Union Territories and all the District Collectorates are connected through this network.

(ii) BSNL - Barath Sanchar Nigam Limited:-
The BSNL is a leading telecommunication company and the largest public sector undertaking of India. It has a network of 45 million telephone lines covering 5000 towns. BSNL provides telecom services.

Emergency Communication
The different modes of emergency communication are
Radio Communication:
(i) Wireless radio communication network
(ii) Amateur radio or HAM

Satellite based Communication system:
(i) Geo - stationary satellites
(ii) Sun synchronous satellites
(iii) SATPHONE

Wireless Radio Communication Network
Electromagnetic waves or radio waves are propagated by an antenna. Radio waves have different frequencies and by tuning a radio receiver to a specific frequency one can receive the required signals.
Frequency bands
• Very low frequency
• Low frequency
• Medium frequency
• High frequency
• Very high frequency
• Ultra high frequency
• Super high frequency
• Extremely high frequency

High frequency bands can travel across the world. This band the radio waves are reflected from the ionosphere.  
Ultra high frequency bands are used in wireless walky talky sets. These play a very important role in emergency communication.

Amateur Radio or HAM
Amateur radio is also known as ‘Ham radio’. The Ham radio works on the same principle as the ordinary radio, the only difference being the user of this mode of transmission has to follow certain frequencies as defined by the International Telecommunication Union. In India the ‘Ham radio is controlled by the Wireless Planning and Coordination Wing of the Ministry of Telecommunication.
Rules to be followed by Ham radio operator
• The frequencies can be used only for research, education and personal use
• The frequencies cannot be used for commercial purposes

HAM radio does not use ground based infrastructure. As it requires limited power supply it runs on batteries. Hence during disasters the HAM radio is used.


Growth of HAM radio in India
There are 15,000 licensed HAM radio operators in India. HAM radio operators are known as Hams. Hams are expected to help the government during emergencies. Their network is used for communication during disasters. Hams are using satellites for communication nowadays.

Amateur radio stations are providing training for people who are interested in becoming HAM operators. The Indian Space Research Organisation (ISRO) has developed HAMSAT, a micro satellite, to provide satellite based services to HAM operators in India and all over the world.
ISRO's Polar Satellite Launch Vehicle, PSLV-C6, launched India's remote sensing satellite, the 1,560 kg CARTOSAT-1, along with a 42.5 kg piggyback satellite, HAMSAT, in a 618 km polar Sun Synchronous Orbit (SSO).
Fig: HAMSAT Satellite in Orbit
Fig: HAMSAT – A Close-Up View  
Satellite Based Communication System
When information is transmitted through a satellite it is called Satellite based communication. Satellites are launched into space on rockets and they are put in orbit. Different satellites carry out different jobs such as weather forecasting and finding accurate locations.

Communication satellites are usually radio relay stations and are referred to as COMSATs. The most important feature of a communication satellite is the transponder.
Transponder is nothing but an automatic device that receives, amplifies, and retransmits a signal on a different frequency. Genrally, a satellite has many transponders.
  Fig: Satellite Transponders

Data, television images and telephonic voice are routinely received and re-broadcasted by the transponders of communication satellites.
Satellite based communication system is reliable during disasters.

Fig:  Satellite Communication System

Communication satellites are in orbit in space and are not vulnerable to natural disasters on earth. Global communication links can be established with very small satellite antennas.

Satellite Phone
The satellite phone is the most widely used means of communication during disasters. These phones provide reliable voice and data communication. They are handy and can be taken to any location.

Satellite Phone
The government of India is providing the Disaster / Emergency Managers of all the districts with portable satellite phones so that proper communication is maintained among the local authorities, during disasters.
Radio communication and satellite based communications are highly reliable and are used during emergencies all over the world.Fig: Search and Rescue Operations through Communication