Sunday, May 10, 2020



Signal control circuit (HR)

The second stage of interlocking is carried out at signal clearance stage i.e. at HR stage. 

To design signal control circuit (HR) the following condition are to be proved. Lets Take off the Home signal S2 to Main line to study those condition.

(At HR stage all the conditions to be satisfied for clearing a signal are proved.) 

  1. The SMs Key inserted and turned to normal to authorised operation i.e (SMR/SMCR (↑))
  2. Crank handles are  ‘IN’, i.e. proved by CHLRs(↑)  and CHFRs(↓).
  3. Sequence Route Release Relays have de-energized after the last train movement (UYR1, UYR2 etc., are down) (In Southern Railways UYR1 and UYR2 are called as TSSLR and TPZR respectively).
  4. No signal cancellation is initiated i.e. JSLR(↓)or JS(↓).
  5. Calling On signal is not initiated, which is proved in case calling ON signal is provided below the Main signal. 
  6. Interlocked LCs if any in the Route and overlap are locked and closed against Road traffic (LXPR (↑)) and held locked till the passage of that train is over. 
  7. Conflicting signals are at ‘ON’ is proved by proving the front contact of ASRs or back contacts UCRs of conflicting signals. 
  8. All points in the route, overlap and isolation are set and locked i.e. Concerned NWKRs, RWKRs are in (↑) condition. 
  9. Concerned to its own signal i.e.
  10. All Back lock and controlling tracks are clear i.e. TPRs concerned are up.
  11. Route Checking Relay UCR is (↑)
  12. One Signal one train movement TSR (↑)
  14. Signal ahead is not blank  (GECR(↑)or RECR/HECR/DECR(↑) in parallel) 
  15. Route Indicator lamps are not lit for straight line (UHRs / UGRs and UECR (↓)) (compulsory in case of Junction type Indicator) 
  16.  Route Indicator lamps are lit for loop lines (UGR or UHR and UECR (↑))
  17.  Sidings in the route & overlap are kept normal and held (siding KLPR/NPR (↑)). 
  18.  Cross protection is provided for the signal control relay, by the Front contact of ASR or Back contact of UCR. These contacts are not favorable for signal clearance. 
  19. Double cutting is provided by UCR(↑)& ALSR(↓)and LXPR(↑)when LC gate is in the route
  20. Signal Button is in Released condition(GNR(↓) )
  21. Signal control relay (HR,UGR, DR) are made slow to release.

Signal Control Circuits HR, HHR, DR, CO-HR

The caution aspect of a signal is controlled by HR.  

Attention aspect and clear aspect are controlled by HHR & DR respectively. 

The ‘ON’ aspect (Red) is maintained through drop contact of HR.  

For Advance starter, the `ON’ aspect is controlled by DR drop and for distant signal the normal aspect (ON) is single yellow, controlled by HHR & DR drop. 

DR Circuit

Let us take OFF signal Number S2, S3, and S11 for Run through M/Ln.

Condition for S2DR to pick up:

1. S2UECPR(↓): its own HR is in picked up condition.
2. 3DR(↑): M/L DR is picked up.
3. 3DECPR(↑): on Negative Line. M/L starter proceed  aspect in burning.
4. Cross Protection is achieved by back contact of 3DECPR.

UGR Circuit:

Whenever a junction type route indication is used on a Home signal and if home is taken off to a loop line, then UGR is energised first.

Then 110 V AC supply is extended to the route lamps and UECR picks up when max three route lamps are burning. Then only HR is picked up through front contacts of UGR and UECR.

CO-HR Circuit:

- Now a days calling on signal are used very widely to increase the efficiency of signal system. Calling On signal is an emergency manager , in the sense that , this is used when the main signal above has failed.

- Calling on signal is taken Off even for receiving a train on an occupied line. therefore it is useful to deal with traffic during track circuit failure also.With calling on signals, the detentions are minimized .

- To study the features of calling on signal HR, let us take OFF calling on signal c-2 B to loop line.

  1.  It is desirable to provide track circuits of a sufficient length in rear of the signal and a time delay circuit to ensure that the CO signal is taken OFF only after the train has been brought to a stop .To achieve this the train has to occupy the calling on track provided at rear of the signal and stop at the foot of the signal . The calling on signal is initiated and cleared after 120 sec.
  2. The calling on signal shall not be capable of being worked at the same time as the main signal above or shunt signal below it, if any
  3. A calling on signal shall  detect all points in the route, which the main signal  above detects excluding those in the overlap.
  4. Route indicator above the main signal is not lit for calling on signal.
  5. It is not required to prove any track circuit in Route and overlap for calling on signal clearance. However other conditions related to interlocking shall be the same as that of main signal above it.
  6. On passage of the train , the calling on route get released on cancellation of calling On signal after a time delay of 120 sec. Sometime a sequential route release may be provided for route release of calling on signal.



  1. Eggnr Smr contact koun sa front ya back use kiya jata hai

  2. I can give you the address Here you will learn how to do it correctly. Read and write something good. Printed Circuit Board

  3. Even standard estimated electrical apparatuses around the home can cause stuns that can kill.
    высоковольтный керамический конденсатор