C
Commercialpedia Indian Railways commercial circulars and policies

Compiled by - S Velraj, Inst/Optg

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TypeCommercial Circular
Topicgeneral
CurrencyCurrency not verified

Summary

| Point Detection | Mech/Elect | Mech/Elect | Mech/Elect | Elect |

Text of the circular

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# INTERLOCKING

Ref        : -  Operating Manual
Signal & Engineering Manual

Compiled by : - S Velraj, Inst/Optg

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Means an arrangement of signals, points and other appliances, operated from a panel or lever frame, so inter-connected by mechanical locking or electrical locking or both that their operation must take place in proper sequence to ensure safety.
# Definition

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It shall not be possible to take ‘OFF’ conflicting signals at one and the same time.
It shall be possible to take ‘off’ signal for a running line only when:-
	All points on the line are correctly set 	and facing points locked.
	LC gates if any are closed and locked 	against road traffic.
Once signal taken ‘OFF’, it shall not be possible to alter the points, to unlock LC Gate etc. until all signals are taken off have been put back.

# Principles of interlocking

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Mechanical Interlocking
Panel Interlocking (Relay)
Route Relay Interlocking
Solid State Interlocking
# Types of Interlocking

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Functions are operated by levers.
Signal taken off only after point is set.
Interlocking between signal lever and point lever.
Signal lever can be reversed only after point lever in correct position.
Size of yards & train movements increased, size of lever frames also.
It occupies more space and requires intensive maintenance.
# Mechanical Interlocking

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Lever frames gave way to relay interlocking based.
Results in faster operation.
Fail safe operation and reduced size of building.
Due to increase in traffic and expansion of railway network, panel interlocking installations were commissioned.
# Panel Interlocking

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RRI is same as panel with eletro mech relays doing the interlocking except that it can be employed for big yards.
Interlocking is between one route to another route.
SM has to only press two buttons, signal & route buttons.
Need not to individually operate the points to the required positon.
# Route Relay Interlocking (RRI)

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Computer based interlocking.
Complex wiring and interconnections (Electro mech relays) not required in SSI.
SSI occupies considerably less space,
Consumes less power
More reliable and is easy to install and maintain.
Initial commissioning and changes due to yard re-modelling can be carried out in negligible time
Unlike PI or RRI, Microprocessors (IC’s) are doing the interlocked base on predetermined logic circuits
# Solid State Interlocking (SSI)

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Increase in section capacity
Faster operation
User friendly operation
Fail safe technique
Multiple mode operation
# Advantages of SSI

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Reduces manpower
Centralized operation
Multiple mode of operation
Control cum Indication panel (CCIP)
Video display unit (VDU)
CTC (centralized Traffic Control) – permits remote control
Significant reduction in traffic block time
Easier & simple operation.

# Significance of SSI for operating staff

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‘Partial’ interlocking means the points at the facing end alone are interlocked with Home signal.

‘Full’ interlocking means the points at facing and trailing ends are interlocked with Home signal.

‘Indirect’ interlocking means points and signals are operated from different places.

‘Direct’ interlocking means points and signals are operated from a particular place.

# Terms related to Interlocking

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Interlocking at stations are of two types
Pre revised and Revised
Pre revised is of three types namely: - Std I, Std II & Std III
Revised standards are of four types:- Std I (R ), Std II ( R ), Std III & Std IV ( R )
# Standards of Signalling and Interlocking

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# Salient features of Pre Revised Interlocking

| Features | STD-I | STD-II | STD-III |
| --- | --- | --- | --- |
| Isolation | Optional | Compulsory | Compulsory |
| Speed over facing points

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