The use of signal arms
Now the signal arms semaphores became widely spread and used in different ways and shapes. The renowned semaphore shapes are the British and the German signal types. Germany uses upper quadrants only while the BR uses depending the line and area upper and lower quadrants.
Issues wtih the lower quadrant:
The lower quadrant signals “falls” or pointing down when showing a clear aspect. When the signal shows a danger aspect, the arm is levelled horizontally. A counter weight has been installed to level the arm horizontally showing a danger aspect. The Upper quadrants does not need the counter weight but the natural gravitational forces pulls the arm downwards without the need of a counterweight. However behind the arm of a upper quadrant semaphore contains mostly a small counter weight is installed to ensure the arm to function properly.
The difference between upper and lower quadrant signals is the position of the signal arm while showing a clear aspect. The position of the upper quadrant signals appoints skywards while the lower quadrant appoints to the ground. The clear aspects always shows off the signal arm in an angle of 45 degrees.
Three position signals
The USA and some countries uses a three position signal showing the main aspects danger, caution and clear. This are the very basic meanings of the three position signals:
-
The horizontal arm shows a danger aspect = Stop,
-
The diagonal arm shows a caution aspect = caution and expect to stop at the next signal.
-
The upright arm shows a clear aspect = clear to pass
More arms underneath each other shows aspects that aims route diverging via designated points. It also regulate the speed of the train unless the speed is given as a stationary speed post. The signals are quite easy to understand and contains very basic regulations.
The PRR used three position signals.
An typical light position signal showing a clearance to proceed driving
The driver should know the route the train has to go, then the driver anticipate on the proper signal. When a signal shows an aspect that does not fit the route the train has to run, the driver contacts CTC using telephone or radio communication and the route and converging signals will be reset. Though the most semaphore signals are disappeared, three position signals are now taken over by position light signals.
The additional white lights adds or change the basic aspects. The position of the white light is extremely important for the proper interpretation of the aimed rule.
A dwarf signal with colour position lights, again the white separate lights on top of the dwarf signal.
If a combination is lights up, a complete different meaning can be given to the original aspect.
The white lights here shows clearly the difference in opposite of the three colour signal.
Searchlight signals
Searchlight signals are one of the best visible signals ever created. At signal boxes the light can be tempered by a switch. At night time searchlight sometimes are too bright to spot. A switch that lead the current via a resistant will reduce the intensity of the light beam.
<< The Dutch federal Railway company used light beam signals since 1946, but he colour aspects are quite different. The white lunar light is the replacement of the high speed.
< Dutch signal showing a caution aspect the number shown here is the speed restriction multiplied by 10. The next oncoming signal does not show a danger aspect.
There is no high speed signal given here is not given here instead a white light eliminates the high speed indication.
The second and the third lights shows a green aspect. The train now has to slow down from medium speed to low speed. Later on this system ceased and merged into a more simpler signal system. The signal are now mostly replaced by the modern Dutch standard signals.
The light beam is highly visible from a far distance.
The 3 colour light mechanic with the small lenses fitted in a half-disc
Interlocking and Signal boxes
Mechanical signals are operated by levers pulling a strain, electro-pneumatic or electric.
Signal boxes contains interlocking systems that prohibit failures in signalling and point settings.
A interlocking is quite simple but still complicated. A simple example: When a point is set into a certain direction, a signal that should give an adverse aspects is impossible by the interlocking system. In IT terms when point X is set to direction A the signal in the opposite direction can not show a clear aspect. In other words: if A=1 then B=0.
An interlocking device. Notice the rod cabinet. An interlocking system in operational order. Mention the notches that locks other rods
The strains pulled by the levers in the signal box are guided through rollers and guiders along and aside the track. A counter weight mechanical device pulls the strain through rollers and guiders to keep the strain tensioned.
A “Reiterstellwerk” above the tracks creating a clear visibility. This type of signal box are often present in Germany. From out of the bridge signal box you a good sight to monitor a lot of tracks around the signal box. The interlocking system is build in the brick shaft that supports the signal box here at the left side of the signal box.
To regain services after WW2, signal boxes were recreated out of available materials at that moment. Old or partly damaged wagons or coaches took over the shelter from signal boxes if destroyed. An example is the bridge signal box that is formed out of former wagons or coaches.
This signal box was formed from a passenger coach for local distances here at Kassel near the Central Station (Hbf)
Take a closer look at the signal box which was the mentioned former passenger coach for local services and is better known as the “Donnerbusch” (Thunder Can)
Straigns and rods
The use of strains and rods is effective in mechanical operation of points and signals. Strains are more flexible but is more inherit to malfunction due to broken strains or malfunction tension devices. Rods however are more rigid but more heavier to operate in the winter period.
Rods and strains pulled by the signal levers in the signal box
Now the signal arms semaphores became widely spread and used in different ways and shapes. The renowned semaphore shapes are the British and the German signal types. Germany uses upper quadrants only while the BR uses depending the line and area upper and lower quadrants.
Issues wtih the lower quadrant:
The lower quadrant signals “falls” or pointing down when showing a clear aspect. When the signal shows a danger aspect, the arm is levelled horizontally. A counter weight has been installed to level the arm horizontally showing a danger aspect. The Upper quadrants does not need the counter weight but the natural gravitational forces pulls the arm downwards without the need of a counterweight. However behind the arm of a upper quadrant semaphore contains mostly a small counter weight is installed to ensure the arm to function properly.
The difference of upper and lower
Three position signals
The USA and some countries uses a three position signal showing the main aspects danger, caution and clear. This are the very basic meanings of the three position signals:
-
The horizontal arm shows a danger aspect = Stop,
-
The diagonal arm shows a caution aspect = caution and expect to stop at the next signal.
-
The upright arm shows a clear aspect = clear to pass
More arms underneath each other shows aspects that aims route diverging via designated points. It also regulate the speed of the train unless the speed is given as a stationary speed post. The signals are quite easy to understand and contains very basic regulations.
The PRR used three position signals.
An typical light position signal showing a clearance to proceed driving
The driver should know the route the train has to go, then the driver anticipate on the proper signal. When a signal shows an aspect that does not fit the route the train has to run, the driver contacts CTC using telephone or radio communication and the route and converging signals will be reset. Though the most semaphore signals are disappeared, three position signals are now taken over by position light signals.
The additional white lights adds or change the basic aspects. The position of the white light is extremely important for the proper interpretation of the aimed rule.
A dwarf signal with colour position lights, again the white separate lights on top of the dwarf signal.
If a combination is lights up, a complete different meaning can be given to the original aspect.
The white lights here shows clearly the difference in opposite of the three colour signal.
Searchlight signals
Searchlight signals are one of the best visible signals ever created. At signal boxes the light can be tempered by a switch. At night time searchlight sometimes are too bright to spot. A switch that lead the current via a resistant will reduce the intensity of the light beam.
<< The Dutch federal Railway company used light beam signals since 1946, but he colour aspects are quite different. The white lunar light is the replacement of the high speed.
< Dutch signal showing a caution aspect the number shown here is the speed restriction multiplied by 10. The next oncoming signal does not show a danger aspect.
There is no high speed signal given here is not given here instead a white light eliminates the high speed indication.
The second and the third lights shows a green aspect. The train now has to slow down from medium speed to low speed. Later on this system ceased and merged into a more simpler signal system. The signal are now mostly replaced by the modern Dutch standard signals.
The light beam is highly visible from a far distance.
The 3 colour light mechanic with the small lenses fitted in a half-disc
Interlocking and Signal boxes
Mechanical signals are operated by levers pulling a strain, electro-pneumatic or electric.
Signal boxes contains interlocking systems that prohibit failures in signalling and point settings.
A interlocking is quite simple but still complicated. A simple example: When a point is set into a certain direction, a signal that should give an adverse aspects is impossible by the interlocking system. In IT terms when point X is set to direction A the signal in the opposite direction can not show a clear aspect. In other words: if A=1 then B=0.
An interlocking device. Notice the rod cabinet. An interlocking system in operational order. Mention the notches that locks other rods
The strains pulled by the levers in the signal box are guided through rollers and guiders along and aside the track. A counter weight mechanical device pulls the strain through rollers and guiders to keep the strain tensioned.