Practice: Signalling
Lower quadrant semaphores
- thanks to Hank Sundermeyer
Lower quadrant semaphores used
yellow blades with black stripes facing traffic.
Lower Quadrant:
Absolute Home signals had square ends and could have 1, 2 or 3 arms.
Aspects:
RRR = Stop, all routes
RRY = Restricting speed, usually a
diverging route
RGR = Clear, medium speed diverging
route
GRR = Clear, main or normal speed
route.
Single arm signal used absolute on route with no divergence.
Aspects
R = Stop
G = Clear
LQ Dwarf always meant
slow/restricting speed route.
Permissive block signals:
2 Arms used in multi track regions.
Upper Arm had pointed blade with
point and was the block home arm.
Lower Arm had fishtail blade and
was the distant arm for the next block.
Aspects
RY = Stop and Proceed at restricted
speed
GY = Approach, next signal at stop
GG = Clear block
Single track regions used one arm block signals
1 Arm block home pointed end
Aspects
R = Stop and Proceed
G = Clear
1Arm distant had fishtail blade. This signal did not convey block occupancy
information.
Aspects:
G = next signal Clear
Y = next signal Stop.
