THE SIGNAL BOX
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The first railway in India (the first in Asia, too) was the Great Indian Peninsular, conceived primarily to improve the transport of cotton to the coast for shipping to British textile merchants, after the 1846 failure of the American crop. The first public train ran on April 16th, 1853.
Early signalling in India was supplied from the UK, so is very British in appearance. However, from the outset, there were differences in the basic principles of the signalling. Signalling instruments seem to have been developed locally, with some ingenious single-line instruments of unique design. One engineer had previously worked on the London & North Western Railway, so some double-line instruments were very similar to LNW products, and a few "stirrup" frames were built locally.
Not all mechanical signalling followed British traditions, though, and some double-wire frames were installed by E W Baker of the Assam-Bengal Railway. This arrangement was also found on the South Indian Railway.
Many wayside stations were signalled in a style more associated with European practice - instruments would be provided in the station office whilst cabins (more in the status of "ground frame") would be staffed only when required. Most of these looked like full-size signal boxes but a few had an open area in place of windows.
At others, extensive use of key interlocking would manage individual hand levers at the points.
Block working of double lines was achieved with (mainly) British-built equipment, although quieter lines simply used Telephone Block. Some busy areas used a Lock & Block system.
On single lines a range of token instruments have been used, the most prevalent being Neale's Ball Token instrument. These instruments were devised by Mr Neale of the Great Indian Peninsula Railway in the 1940s and have become widely used in India, and in a few other countries. Some have been manufactured by Westinghouse. Some electronic systems have been developed to work single lines without tokens.
The Following Trains system of operation was introduced during the Second World War to boost the capacity of busy single lines. Under this system, freight trains may follow each other through a section at fifteen (or more) minute intervals. Drivers of such trains are issued with written instructions.
The US term of Automatic Block Signalling is used for the equivalent of British Track Circuit Block.
Earlier power installations were provided with American three-position signalling; working in the upper quadrant. All other semaphore signalling operates in the lower-quadrant.
Modernisation has seen the introduction of colour-light signalling - both in multiple-aspect from and position light signalling. The latter are not position light shunting signals (as in British terminology) but US-style multiple-lamp signals that show their indication using combinations of lamps of the same colour. Multiple-aspect signalling uses the same basic four-light system as the UK, together with junction indicators for divergences.
Although in many places the signalling has now been modernised, mechanical signalling in India does survive in respectable quantities.
Additional notes by Rajendra Aklekar