Indian Telephones 

Calcutta was the British Capital of India, when the first Telephone service arrived in India. The trunk-lines were gradually installed between large metros. Pune and Hyderabad C-8 line was an example to that effect. To multiply the channels, repeater stations were installed on the route-way, like one at Humnabad, another at Zahirabad etc. The Pune -Hyderabad route had many repeater stations. They were needed for signal amplification between the metros linking trunk lines. So erection of physical lines was a need of the hour. Lot of man-power was engaged and later recruited as line staff. These things repeated all over Indian sub-continent. The system started expanding even to large villages, to open Public Call Offices[PCOs] during 1960-70s period. This system was called open wire system of communication.
Then came the era of under ground cables for local lines. Since each telephone line needed two conductors separately, right from The central telephone office to subscriber's premises, cabling was a must for local individual subscribers lines. Coaxial cables were installed between cities for multiple channels. Then the microwave towers arrived to replace C-8 lines all over India during 1980s. The Bangaluru-Nagapur microwave route is an example.
The  1990s saw the installation of Optic Fiber Cables [OFC routes] all over India, as the final networking system between all cities and towns. This enabled us to extend internet services to the general public in 1999 in India. A gate-way switch was installed in Mumbai for this purpose. This period is also called mobile telephony era. The all earlier wire systems were gradually disappearing. Private service providers were licensed by the Indian government to make the services competitive and  cheaper. BSNL was created out of DOT as a service provider. Now[2019], all most all adults in India hold a personal mobile set to communicate at affordable rates.

Telephones landmarks [India]

1876-The telephone was invented in USA.

1881-The Oriental telephone company, was licensed to open telephone exchanges in India

1882- First Telephone exchange was opened in Calcutta, Bombay, Madras and Ahmadabad.

The central exchange Calcutta had 93 subscribers.

1907-First central battery telephone exchange installed at Kanpur.

1913-14- Automatic telephone exchange opened in Simla, [HimachalPradesh].

1927-Radio Telegraphy started between India and UK.

1933-Radio telephony started between UK and India.

1953- A 12 channel carrier system was installed for trunk working in India.

1960- The STD service between Lukhnow and Kanpur was commissioned.

1975- First PCM system installed between Bombay and Andheri, for local junction working.

1979- The OFC [Optical fiber cable] system was installed at Pune, for local junction working.

1984- C-DOT [committee on development of Telematics] established for manufacture of digital switches.

1995- First mobile telephony service started at New Delhi.

The department of posts and telegraphs was owned by Central Government of India. The telephone exchanges were controlled by P and T department. Post Master General was the head of a circle. Indian telephone industry [ITI] was the public sector company to manufacture the system requirements of Telecommunications.

1985-DOT [Department of Telecom] was separated as independent department.

1986- Mahanagar Telephone Nigam [MTNL] and Videsh Sanchar Nigam [VSNL] were separated.

Microwave towers were installed along the length and breadth of the country as trunk routes. STD services were extended to District headquarters. Digital exchanges were manufactured and large scale expansions were carried out with modern switching centers. OFC cables were buried throughout the nation for trunk services.

Liberalization activity started to meet the demand of the general public.

1997-TRAI [Telephone regulatory Authority of India] was constituted.

2000-TDSAT [Telecom Dispute Settlement and appellate Tribunal] was formed.

The Operating wing of DOT was converted into a corporation called Bharat Sanchar Nigam [BSNL].