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General Annexure: G4
GLOSSARY OF TECHNICAL TERMS FOR SIGNAL ENGINEERING MANUAL
S No Term Description/Meaning in SEM Relevant paras
1 Act Means the Indian Railways Act, 1989 3.5.4, 9.1.1(a)(i)
2 Adequate Means the distance sufficient to ensure safety. These are known as overlaps in signalling 7.1.8, 7.1.9, 7.1.15,
Distance context 7.4.9, ,12.5.4(a),
20.1.4(a)
3 Advance Section between Intermediate Block Signal and First Stop Signal of station in advance 18.12.1, 18.12.4,
Section (including block overlap) Annexure: 18-A4

Approach Means an arrangement in which the lighting of signals is controlled automatically by the
4
Lighting approach of a train.
5 Approach It is a locking provided on points in the route, overlap, isolation (as applicable) to prevent 7.6.2(a), 12.28.2(c),
Locking/Dead their unlocking or operation of Points in the face of a train, approaching a stop/shunt signal in 14.1.7(d), 14.1.9(b),
Approach it`s OFF position, such locking shall be effective even if such signal is put back to ‘ON’ 19.8.9 ( b, c),
Locking subsequently till lapse of defined time period. (Explanatory notes: Approach locking shall be 19.8.11(b), 20.2.3,
effective from a distance which is not less than maximum emergency braking distance of a 21.1.4(f), 21.1.6(i),
train running at maximum permissible speed in that section, approaching a stop signal. For a 21.1.9(d)
home signal, such approach Track commences from concerned Distant signal/Inner Distant
signal in rear to Home signal. In the absence of such an approach track circuit, Dead
approaching locking is provided with a timer to prevent any unlocking of the said points)
Approved
6 A set of guide lines issued for a specific purpose after due approval by competent authority.
Guide Lines
Approved Special instructions approved of or prescribed by the Commissioner of Railway Safety (CRS) 7.1.8, 7.1.9, 7.1.16,
7 Special 7.1.17(a,b), 12.5.4(a),
Instructions 12.5.8(b) 20.1.1
Approved A technical specification approved by RDSO/Competent authority 16.4.1(a,f), 18.1.1(d),
8
Specification 21.3.1(f), 22.4.4
Approved Type An equipment/component which confirms to specification issued by RDSO/Competent 7.6.9(d), 14.2.1(b),
9 authority 17.2.10(a), 19.2.1(a),
21.2.1(a)

Annexure: G4: Glossary of Technical Terms for Signal Engineering Manual Page 514 of 535