ITHIHASA - A 100000 Years Story of BHARATH (INDIA) - Documentary English...

सोमवार Special शिव महामृत्युंजय मंत्र, Mahamrityunjay Mantra 108 बार,Mea...

 

The human voice on wires:

simply using two insulated iron wires overhead along the streets, a human voice could be transmitted as an electrical signal generated by a telephone apparatus. if all such wires are terminated on a board, the board operator[also called telephone operator] could manually interconnect these lines as required by a service user at any time. This constitutes the simple theory of a telephone exchange. If the power supply needed to run the system is supplied from the central office itself, it was called central battery exchange. such service evolved in the USA long back after 1876 in Bell's lab.

This network device made things easy to communicate immediately in a local area between business offices and homes as needed. The distance of telephone lines could be increased to talk with nearby villages by erecting thick weld copper conducting materials. For a local area, about five kilometers radius was standardized; beyond that, the voice would be very feeble to hear. fifty volts DC battery was used to run the system. one such system was installed in Calcutta during British rule in India with less than 20 lines to start with. The system was gradually expanded to other presidencies like Bombay and Madras.

Over the time, some new innovations were made and the facilities were expanded to many princely states of India. Many such CBNM and CBM systems flourished all over India before Independence.

To interconnect the switching centers, trunk lines were constructed.

At the time of independence, when all princely states were integrated into a single Nation as India, a department was created called DOT.

After the next two decades, when electronic diodes and transistors were made available, for the first time, the voice modulators and demodulators were manufactured and used successfully to carry more than one telephone speech over the same pair of wires, between the neighboring towns and cities. These were called speech channels.

A standard three-channel system was evolved to make it possible to run four voices together on a single pair of wires [called NCJ lines]. Later the channel capacity was increased to eight channels on C-8 trunk lines. During the 1970s, One such system was working between Pune and Hyderabad which was constructed along national highway number nine. Repeater stations were installed to increase the power loss due to transmission lines. These stations were also used to drop or inject a channel at local exchange office. This served to branch the system as needed.

The business community and the government functioning were the first users of this system.

Gradually almost all the district places and important towns got telephone services in India.

Automatic local exchanges were developed using electromagnetic relay logic systems. One 200 lines switch needed one large room to house all accessories like the battery and power plant. It would take six months to commission one such system. 50-lines switches were used for smaller towns. The 1980s saw this development in India. After 1980, the efficiency of the telephone service increased. The switching capacity expansions started regularly to increase the services to rural areas too. Gradually, the villagers started using the telephone facility. The government thought that there should be at least one telephone in a village for communication. Many public call offices were opened. The DOT was separated from Postal services.