Semaphore Signals Background

The roots of the present German Railroad (DB) Semaphore signal system can be traced back to the earliest days of Germany's railroading history. This signal system is based on a set of shape signals (Formsignale in German) in combination with colored lamps, similar to the flags and lanterns used in provincial times. These signals are chiefly mechanical, with their aspects operated by metal cables and their lamps fueled by gas. The high maintenance associated with these signals caused them to be slowly replaced by electrically-operated color light signals on most mainlines throughout East and West Germany following World War II. To this day, however, Semaphore signals can still be seen on the DB in and around many station areas, where they are maintained by the crew of the local station.

The Semaphore signal system is very straightforward in its operation, with only three major classes of signals: main, distant, and yard. Main signals stand just before the immediate point of danger, such as a crossing, turnout, or block entrance. A distant signal is placed some distance, usually 1000m, ahead of each main signal to display its setting in advance. Depending on the distance between two main signals, the distant signal for the second may be grouped together with the first main signal, either standing in front of or directly adjacent to the first main signal. This is common practice on station tracks and on mainlines with high traffic and short blocks. To protect the sidings that flow into station tracks and control switching maneuvers, yard signals are placed at their exits. Yard signals are also used in other applications, such as to guard the entrance to moveable railroad bridges or transfer/turn tables.

Main signals (Hauptsignale in German) are also sometimes called "home" signals, since they are placed just ahead of a danger point. There are three basic types of main signal: block, entry, and exit.

A main block signal is used exactly as its name implies, to control train movements in a mainline block system. Each signal protects the entrance to its respective block, providing a safe distance between an approaching train and the train occupying the block. These signals have a single movable arm and a pair of lamps, which can show only two aspects, Stop or Proceed.

Hp0:

Stop

Hp1:

Proceed

A main entry signal is placed wherever reduced speed is required, such as the entrance or exit of a station or passing siding, which usually includes branched turnouts. The second movable arm and third lamp on the entry signal shown below can display a third aspect, Proceed Slowly, which establishes a 40km/h (25mph) speed limit in these areas. In situations where no straight-through operation is possible or a speed limit is always imposed, a main exit signal may be used instead, which can show only the aspects Stop or Slow. This is often the case on station exit tracks where a long turnout area follows and speed is governed by a "Zs3" speed indicator board.

Hp0:

Stop

Hp1:

Proceed

Hp2:

Slow

Distant signals (Vorsignale in German), also called warning signals, give the locomotive engineer an advanced indication of the aspect of an upcoming main signal. They are usually placed 1000m ahead of their respective main signal. In accordance with the main signals described above, there are three corresponding types of distant signals: block, entry, and exit.

A distant block signal has two pairs of lamps along with a movable disk, and can display the aspects Expect Stop or Expect Proceed. These signals are used on mainlines to announce the setting of the next main block signal.

Vr0:

Expect Stop

Vr1:

Expect Proceed

Distant entry signals are also equipped with a movable arm, in addition to the two pairs of lamps and movable disk of distant block signals. These signals are used to announce main entry signals that stand before areas where reduced speed may be required, such as stations or passing sidings with branched turnouts. The movable arm on the distant entry signal displays a third aspect, Expect Slow, 40km/h or less. The distant exit signal is similar, except it has a fixed disk and can display only the aspects Expect Stop or Expect Slow. The distant exit signal announces a main exit signal installed on a track with a maximum permissible speed of 40km/h or less.

Vr0:

Expect Stop

Vr1:

Expect Proceed

Vr2:

Expect Slow

Every distant signal is designated by an "Ne2" board, as indicated in the illustration below. The "Ne2" board is a fail-safe that tells the engineer to Expect to Stop in the event that the signal is malfunctioning or its visibility is otherwise obscured. When a distant signal must be placed closer than 1000m to its following main signal, the resulting reduction in braking distance is communicated to the engineer by a small white inverted triangle located above the "Ne2" board. Additionally, all distant signals are preceded by a set of three signs, known as "Ne3" distant indicator boards. Each board has one, two, or three black stripes on a white background and usually stand in front of the signal by 100m, 175m, and 250m, respectively. Just as before, if the distant signal is at a reduced distance to its main signal, the first "Ne3" board (with three stripes) will also have an inverted white triangle above it.

In high-traffic areas, most often at or near stations, distant signals may be placed immediately in front of or beside main signals. This is very common at station entrances, where the station tracks are not long enough to accommodate the required distance between a distant signal and its subsequent main signal. In this case, the distant exit signal may be located directly near the main entry signal. For safety reasons, whenever the main signal shows a Stop aspect, a distant signal in front or beside will be switched to Expect Stop, regardless of the next main signal's setting. Since the train must stop at this main signal in any case, an advanced indication of the next main signal is not necessary and may only lead to confusion. Once the main signal has been switched to a Proceed or Proceed Slowly aspect, the correct distant signal setting reappears.

Track block signals (Gleissperrsignale in German), also referred to as yard, shunting, switching, or track protection signals, have several applications in yard and station areas. Most often, they are used to guard the exit of a track siding and to control shunting movements. The yard signal can prohibit or permit shunting with its two aspects, Sh0 and Sh1:

Sh0:

Shunting Prohibited

Sh1:

Shunting Permitted

There are two basic configurations of the yard signal, the dwarf type and the mast type, as illustrated above. The shorter dwarf signal is often used in areas with tightly spaced tracks and less danger, such as a freight or storage yard. If the signal is protecting the exit of a siding that leads directly into a station track, it is usually mounted on the mast to improve its visibility. This is also the case if yard signals are used to protect the individual sidings within a group, which has only one exit signal. The yard signals then indicate to which track in the group the main exit signal applies.

When installed on station exit tracks, yard signals are often used in combination with main signals, as illustrated below. Here, the main signal will show Stop for train movements, while the yard signal controls the shunting movements. In order for train movements to proceed this signal combination, however, the yard signal must also indicate permission to proceed (Sh1) in addition to the main signal showing a Proceed or Slow aspect.

Hp0; Sh0:

Stop;

Shunting Prohibited

Hp0; Sh1:

Stop;

Shunting Permitted

Hp2; Sh1:

Slow;

Permission to proceed

Aside from their usage in the yard, these signals are often found next to long station platform tracks to divide them into multiple segments for shorter local trains. This allows a higher frequency of trains entering and exiting the station area without requiring additional tracks. In some instances, yard signals are also used to protect the entrance to moveable bridges, turntables, or transfer tables as well.

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