Signalling - Part 1 Flashcards
Name the 3 main modes of signalling?
TCB - Track Circuit Block
AB - Absolute Block
TB - Token block
What is the principle of ABSOLUTE BLOCK signalling?
One train in one section at one time
What is a SASPAD?
Starting Against Signal Passed at Danger
Name the 3 signals within a block section?
Section
Distant
Home
How amazing is Liam?
Truly fantastical and wonderfully phenomenally amazing! (I’ve been hacked!)
What is a clearing point?
A 400m clearance point at the start of the station limits which the train needs to pass before previous signal can be cleared. Basically, a buffer!
The block section and the clearing point must be clear before another train is permitted to enter the block section.
What are the station limits?
The portion of line between the first ‘home’ signal and the ‘section’ signal under the control of one signal box
What is a block section?
The portion of line between the ‘section’ signal of one signal box and the first ‘home’ signal of the next
(A BLOCK of FLATS is SECTIONed into HOMEs)
What does the symbol with a horizontal line, and a dot above it, mean?
Signal box
What does a semaphore signal with a white diamond underneath it mean?
Presence of track circuit (TCOCs will advise signaller the section is occupied)
What does a white diamond or a yellow diamond with a “T” in it mean?
Signal is equipped with a telephone
What is the principle of signalling?
One train, one section, at any one time
What do the 3 colours mean?
Red = danger
Green = proceed
Yellow = proceed with caution (Be prepared to stop short of any obstruction)
What does the symbol of a horizontal line with a dot above it mean?
Signal box
What does a subsidiary semaphore signal with a C displayed mean?
Calling on - You can proceed (to the sidings) but the line ahead may be occupied
You must proceed cautiously and be able to stop
What does a subsidiary semaphore signal with a S displayed mean?
Shunt - Proceed at caution only as far as necessary to complete the move
These may be found near a yard or a siding
Describe a shunting signal on stop?
A circle with a red horizontal bar
Red light will show at night
Describe a shunting signal on proceed?
A circle with a 45 degree red bar.
Green light will show at night
Describe how STEPPED signals work
The highest signal relates to the main route
Lower signals relate to progressive routes to the left or right of the main route
Describe how STACKED signals work
The highest signal relates to the furthest left of the line.
The lower signals relate to lines from left to right. Eg, top signal (1) furthest left, second signal down (2) middle line, lower signal (3) right hand side line.
Is a semaphore signal at a 45 degree angle ON or OFF?
OFF
Describe the service braking distance
The distance between the ‘distant’ signal and the ‘home’ signal
What is the size of the clearing point?
400m
Describe an intermediate block
When a block section is very long this is not very efficient as only one train can enter at any one time. Intermediate block sections were introduced to mitigate this. These are usually colour light signals but still on the semaphore signal routes
An intermediate block DISTANT signal and an intermediate block HOME signal is added after the SECTION signal. These are always controlled by the box to the rear of the signals
What is a FIXED DISTANT signal?
