Signaling layout

Railway Signal Clearance RRI

Indian Railway Signalling

Railway Signal Clearance RRI

Signaling layout

Signaling layout

Point free to operate



Point free to operateRoute setting

1. First button pressed is recognized as entrance button and the second pressed  button is recognized as exit button.

2. Prevents conflicting routes from being set.

3. Prevents points being set to other than the required position.

4. Locks individual points in the required position.

5. De-energises route stick relays (USRs) in the route including locked overlap, if any, thus making the route locking effective.


Signal RLR

Energised when-

1. Points are initiated to set to the required position if not already set.

2. Points will move to the called position

3. After points are set to correct position and locked the detection relays NWKR/RWKR will pick up.

Route initiation circuit -1

Route initiation circuit -1

Route initiation circuit -2

Route initiation circuit -2

Point initiation circuit

Point initiation circuit


1. Proves all the controls defined in the control table –

2. the route  requested is set & locked,

3. Overlap locked where required,

4. All points in the route including overlap are detected in appropriate position, and locked electrically,

5. track sections in the route including overlap are clear

6. Approach releasing tracks occupied where required,

7. lamp of signal ahead lit,

8. Signal stick controls GSR energised,

9. Any other special conditions are fulfilled.

10. When above conditions are fulfilled final signal control relay GR energises. This allow the signal to clear to a less restrictive aspect


Special controls

The back contact of the last USR is proved that entire route is locked.

Special controls as specified in control table –

1.override controls/slots

2.Aspect disconnection links  for individual routes.

3.Finally approach control timer down is proved on negative side

4.Track occupation which inhibits signal replacement $40. Last wheel replacement

5.Controls proved only at the time of clearance $10


GSR circuit

GSR up contact ensures that the signal cleared for    a train is withdrawn after train passing that signal. Signal should clear only after the route is set again.

GSR circuit

Signal control circuit

Signal control circuit

Approach locking circuit-1

Approach locking circuit-1


Approach locking circuits -2


Approach locking circuits -2


Route normalisation circuit – NR

Route normalisation circuit

Over run controls

1. Over run of any signal likely to cause collision with legitimate move.

2. To prove no SPAD occurred. Should it occur, the signal restored to “ON”. The signal shall not re- clear unless the whole track section is cleared by train which SPAD.

3. Bi-directional controls proved

Auto controls

Auto SR circuit. When the signal is set for auto working a special relay Auto SR picks up.  This energises the GSR automatically after passage of the previous train.

Swinging Overlap

After a signal is cleared –

1.Facing point in the overlap is allowed to swing to set an alternate overlap.

2.OSR relay permits to hold GR for 5 secs to allow swinging of overlap point to other position.

3.Signal is reverted back to ON position if point fail to respond to other position within the specified time.


Two red rule

1.When the Junction Protecting (inner) signal route is set, the Full line Speed signal is cleared to free yellow.

2.When the Junction Protecting (inner) signal route is not set, the Full line Speed signal is cleared with MAR.

When approach cleared.




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