JeffPo's Semaphore Lamp Page

Original Post:  11/09/16

Last update:  11/16/17

This is a semaphore lamp made by the Dressel company.  The company name is stamped on top of the lid.  It has a single clear/white lens, of about 5 inches in diameter.  The lamp itself stands about 15 inches high, not including the handle.

To access the burner, you slide up a side panel/door.  The lamp housed a long time burning fuel fount.  Unlike the order lamps that were near the depots and stations, some semaphore lamps were more remote so they needed to burn longer in between fuel fill ups.  There are also two peep sites, one on the side and one on the door panel, so that the person tending to the lamps could glance to see the how the flame was burning.  The wick adjustment knob on the burner extended outside the lamp frame such that you could adjust the flame height without having to open the door.

The rectangular sleeve on the side is hollow (the bottom is open) and was used to mount the lamp behind the semaphore signal spectacle.

While almost all hand lanterns were marked for the railroad that were used on, I haven't seen this practice used as much with lamps.  However, this lamp is marked with a tag reading P.R.R. CO which means this particular one was used on the Pennsylvania Railroad.  Look below for a brief history of the Pennsylvania Railroad.

This semaphore signal has an electric lamp for roundel illumination.

The kerosene powered semaphore lamp was used to illuminate the colored roundels on a semaphore signal at night.  The roundel lenses on the semaphore spectacle were colored green, yellow, or red, hence why the semaphore lamp had a clear lens.  Sometimes you will encounter a semaphore lamp that has had its clear lens replaced with a yellow lens.  This is a case of a semaphore signal being permanently set to show a reduced speed aspect.  The yellow roundel would be removed from the semaphore spectacle and a yellow lens placed on the semaphore lamp in place of the clear one.  The semaphore blade would also be locked in place to always show the reduced speed aspect.

Eventually these semaphore lamps were either modified to be electric, or replaced with an electric version of the lamp (like you see in the above image).  Colored light signals eventually replaced semaphore signals all together.  Look below for a more detailed description (that really only scratches the surface) of how semaphores signals were used.

Semaphore Signals

Semaphore signal on the Santa Fe Railroad, 1943.

The semaphore was one of the earliest forms of fixed railroad signals.  They consisted of a blade, attached to a spectacle with colored glass roundels, mounted to a tall pole (or signal "bridge") that by being displayed at various angles could signal various instructions to the engineer driving the train.  They used the illuminated colored roundels for nighttime use.  Semaphore signals were patented in the early 1840s by Joseph James Stevens.

Parts of a Semaphore Signal

Here you see a typical semaphore signal.  Hover over the image with your mouse pointer to see the parts labeled (or click THIS LINK).  For perspective, the overall length is about 5 to 6 feet or so.  The semaphore signal consisted of a spectacle that held a number of colored glass roundels, and a blade that stuck out.  The colors of the roundels would be green, yellow, or red.  Remember that the yellow flame of the kerosene burner would make the aqua blue colored glass shine with a green hue.  The blade could be different colors, shapes, and lengths depending on how and where it was used.  The number of roundels also varied depending on use.  A stationary lamp with a clear lens was used to shine through the roundels for use at night.  The semaphore lamp was attached to a mechanism that would rotate about the hub, to change the angle of the blade, and to bring the desired colored roundel in front of the lamp to be illuminated.  The angle of the blade and color of the light signaled different orders or conditions to the engineer of the train.

Samples of Semaphore Signal Positions

This image shows a semaphore signal at the top of a pole.  There's a light source behind the spectacle, for shining through the roundels, to give illumination at night.  Generally the blades could move in one of two directions from the horizontal.  If they moved up from the horizontal position they were known as upper quadrant semaphores.  If they moved down from the horizontal position they were known as lower quadrant semaphores.  There could be multiple semaphore signals on a pole.

The following partial images were taken from a 1925 Pennsylvania Railroad rule book.  They represent a very simple look at how semaphore signals were used.  They were actually much more complex, and could be used in multiples to convey more complex messages and signals.

This signal is showing the proceed or all clear signal.  The blade is fully vertical (0 degrees), and the illuminated roundel is green.  Given this one has moved up from the horizontal position, it's an upper quadrant signal.  You could have multiple semaphore signals on a single pole.  Had this been a lower quadrant semaphore, the blade would only move from the horizontal position downward, and would be pointing straight down, while still displaying a green light.

This signal is showing a slow or restricted speed signal.  The blade is at a 45 degree angle and the illuminated roundel is yellow.  Had this been a lower quadrant semaphore signal, the blade would be pointing at 135 degrees from vertical, but still showing a yellow light.

This semaphore signal is showing a stop signal.  The blade is horizontal (90 degrees from vertical) and the illuminated roundel is red.  Typically the horizontal position was always a stop signal, whether or not it was an upper quadrant or lower quadrant semaphore.

Semaphore Evolution and Today

Author's image of a Baltimore & Ohio style Color Position Light signal:  Gaithersburg, MD, 01 Nov 2008

The use of mechanical arm signals were phased out in favor of color light signals.  Once such device was the Color Position Light signal.  They simulated the aspect of a semaphore signal arm with lights.  The Baltimore & Ohio version added color to their Position Light Signals.  The two lights in the horizontal line would be red for stop.  The 45 degree angle lights would be yellow for reduced speed, and the vertical lights (ie. the one at the top and the one at the bottom) would be green for all clear.

Here's another example of the Baltimore & Ohio version of color position light signal, showing how color was used with the simulated angles.


Color light signals make up the vast majority of signals used today.  Semaphore signals have gone extinct.

More Information

As I mentioned before, what I've shown here is a very simple view of the basics of semaphore usage.  To really dive deep into the complexity of semaphore signals, visit the following excellent webpage on the subject::  Webpage by Todd Sestero

My Semaphore Signals

Semaphore #1


This is a lower quadrant semaphore signal, meaning that from a horizontal position it moves downward.  It has three colored glass roundels, which are red, yellow, and green.  The blade portion is 42 inches long.  When you include the cast iron spectacle (the part that holds the glass roundels) the entire semaphore signal is about 68 inches long.  It's quite a hefty piece, weighing 63.3 pounds.

Semaphore #2


This second semaphore is an upper quadrant semaphore signal, meaning that from a horizontal position it moves upward.  It has three colored glass roundels, which are red, yellow, and green.  The blade portion is 48 inches long.  When you include the spectacle (the part that holds the glass roundels) the entire semaphore signal is about 77 inches long.  The spectacle on this one is made differently than the first one.  It isn't as thick.  While it has some weight, it's not as heavy as the other one.  This ones weighs 45.7 pounds.

Pennsylvania Railroad

Pennsylvania Railroad M1a locomotive on display at the 1939 New York World's Fair.

The Pennsylvania Railroad Company was chartered in 1846 and had completed a track to Chicago by 1856. By the end of the 19th century, the Pennsylvania Railroad Company had expanded to St. Louis, Missouri, and Cincinnati, Ohio, in the west and to New York City, Washington, D.C., and Norfolk, Virginia, in the south and east, ultimately becoming a 10,000-mile system. Although it had prospered in the early part of the 20th century, by the 1950's it was losing considerable money annually. In 1968 the Pennsylvania Railroad merged with the New York Central Railroad and created Penn Central Transportation Company, which later absorbed the New York, New Haven and Hartford Railroad Company. The company's holdings have since been split among Conrail and Amtrak.

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