Graphic and Geometric Signals
Terminology, Types of Signals and Signal Functions
This segment encompasses a broad spectrum of signals less than wholly-lighted and neither semaphore nor signal board. They produce messages by geometric or by graphic means. Since so many of these siganls deal with switch/point functions and/or with shunting functions it would have been reasonable to term this segment Switch and Shunting Signals but in keeping with the perspective of the transportation markings monographs, the first concern is the signal then the message and its context.
Since some shunting and point signals are also found in Chapter 31 it may be helpful if the reader reviews that material and also Chapter 31 wherein all-lighted forms of shunting and switch signals are considered.
Each of the these signals bear two of four basic characteristics (and the characteristics can be paired); the signals either rotate or they revolve, and the night/day portion is either an integral unit or a separate unit. If a signal revolves then all, or a significant portion of the signal unit, turns on an axis. If it rotates then actual signal-producing component turns (similar to the motion of a clock). If the day/night aspects are an integral unit (as in a disc signal) then both portions are always present. U.S. targets, however, share a common base or signal mast but the signal lamp may be absent from the day targets.
The major functions of graphic and geometric signals are as shunting and switch/point indicators. In many systems there are specific shunt signals covering low-speed movements on mainlines and to and from mainlines; it is possible that train movements in marshalling yards and other special situations can be encompassed within the shunting function. Shunting signals by that name may not be known in North America but the shunting function is carried out by dwarf signals or by the low-speed indications within regular signalling. Of course many of these signals are fully-lighted and not covered in this segment.
The second major function is that of switch/points indications. This function is virtually universal. Indicators are found at junction of tracks; intersections of main tracks, main-secondary tracks, marshalling yards and other situations. In some instances these are termed signals while in others they are indicators (McLean notes that signals give messages of proceed, etc. while indicators denote direction to go; this is the case for some systems it is not for others; McLean 1990) . Signals in a given system may or may not include these markings as an integral component.
Terms for shunting signals in a variety of languages bears a striking resonance: Romance language terms include Manoeurvre (French), Maniobra (Spanish), Manouva (Italian), and Manobras (Portugal). Even several languages well removed from the Romance tongues employ similar terms: Manowrowa in Poland, Manevrisanje in Yugoslavia, and Mahebopobon in the USSR. German language codes employ Rangiersignal, and the Netherlands, a similar Rangeersein. Belgium speaks literally of petit mouvements. The English language has settled on shunting.
As has been noted, there are two terms for the juncture of tracks: switch, and points; thouugh they refer to the same function. This divergency in terminology is reflected in the variety of terms in other languages: France has Signal de position while Spain uses Indicador de posicion (SNCF 1981, RENFE 1978). Italy uses Segnale indicatore and this is echoed by Portugal with "Indicador de posicao de agulha" (indicator of the position of switches) (FS 1983, CP 1981) .
German language codes use weichensignale and the Netherlands, wisselsein (IUR/UIC Gen. Diet. 1975, 914). North America uses switch stands and switch signals. More often, other English-speaking nations employ points indicators. There is a marked degree of uniformity of function if not terminology for these markings. Switch indicators can also refer to track indicators and their relationship to switches.
Geometric Signals
Geometric signals are within the 532.52 and 533.54 and 533.60 categories of the classification. All of the geometric signals will be encompassed in this segment. In the classification revolving or two-sided signals are separate from rotating or single-faced signals. In this coverage they will be conjoined since they share notable similarities. Other rotating and revolving signals will also be included. The other remaining portion of geometric markings are the targets found in North America, parts of South America, Australia and Asia. The rotating discs offer four forms. The most common is a disc signal with face and a simulated semaphore bar mounted on the disc. The signal lamps are behind the face and shine through an opening in the face; the color appearing depends on the position of the disc. A second form lacks internal signal lamps but is instead indirectly lighted by a flood lamp attached to the signal that acts as a substitute for daylight; this means that day and night messages are one and the same. A third form, though not termed a disc signal, is a glass-enclosed arm or bar within a circular housing. This is termed a banner repeater in the U.K. (U.K. K&W 1963, 22). The partial disc constitutes the fourth form. Despite its truncated disc it closely resembles the message capabilities of the full model.
Revolving discs are marked by greater diversity. This signal form has at least five versions. One version has discs of equal size for both stop and proceed sides; another has discs of unequal size for the faces; a third displays a disc on the stop side and a horizontal band on the proceed side. Yet another has a non-message or "blind-side" for the proceed (just as some signal boards have a non-message side for proceed messages). Finally one form has a disc for stop and an upright rectangular bar for the proceed side. Discs in Victoria are on signal masts and therefore not dwarfs though they are for shunting purposes (VR-A Wooley 1958-1).
The functions for these signals are primarily shunting, and points indication. But it is not easy to divide the signals into a single function. The message segment of this chapter provides some information on signal function.
There are two geometric signals affiliated with the disc signal for QR that perform much like a disc signal. These signal display arrows on both faces in one model and solid on one face and arrows on the other face in the second model (NSW 52).
The U.K. and derivative systems also include two geometric signals without a special day target. In both cases the signal housing, or the metal framework affixed to the housing serves as the day indication. In one form the housing (termed panel by this compiler) is of a single color with one signal lamp for each indication; the second form is divided into two color panels with accompanying signal lamps. Each panel represents one track. The color patterns are applied to the housing (red and white; QR 1965) .
The disc signals so far considered follow a largely unvarying pattern dating back in some instances to Victorian and Edwardian eras. Even though on the wane it continues to find considerable use (see for example the 1900 catalogue of McKensie and Holland). Another form of geometric signal also has Victorian antecedents but with many more variations and therefore more difficult to briefly sum up. This signal is the open target previously mentioned and which is most commonly found in the U.S. The day and night portions, though sharing a single mast, can easily be separated and thereby exist independently of one another. Since this is a simple marking to manufacture this adds to the difficulties of comprehensively reviewing it. Patterns in transportation markings often maintain certain forms over many years which suggests there is a limited range of designs in use. This signal is definitely and visually different from switch and points indicators of U.K. and U.K.-influenced systems, and indicators in Europe.
The free-standing target is not covered by a central code. A U.S. railway engineering group provides a listing and illustrating of design shapes and at least one manufacturer provides a pictorial catalogue of shapes (Bethelehem Steel 1981). This is the case in the U.S. but it is less true for other systems such as ANR and JNR (ANR 1947, JNR, 2-8) where a more restricted range of shapes are approved and in these instances a certain standard is followed.
Graphic Signals
There is uncertainty, at least for this compiler, about the placement of graphic signals: are they to be considered partially-lighted or fully-lighted? This question does not arise with most other railway signals. Fully-lighted signals, for example, are all-lighted, and most partly-lighted signals are clearly partly-lighted and partly-unlighted. There is no problem in determining the character of those markings or of distinguishing between lighted and unlighted dimensions.
However, graphic signals have an uncertain character since two separate signal message properties of graphics and lighting are nearly fused together: there is no day part separated from a lighted part. In a geometric disc signal the disc is one element, and the signal lamp is another, while in an all-lighted signal the signal lamp constitutes the entire message apparatus. But the graphic signal has one shape whether unlighted or lighted.
Nonetheless - despite their uncertain character - an examination of pertinent signal codes can suggest an approach to graphic signals for this study: it is possible to subdivide these signals into two forms: one fully-lighted, and one partly-lighted based in a logical pattern. In the first form, internal lighting is required for both day and night indications. In this form the graphic representation (usually an arrow though of a variety of design pattterns) can not be seen when unlighted unless the viewer is quite close to the signal. In the second form it is possible to see the graphics in daylight without internal lighting and at some distance from the signal. Many examples of the first form are found among double-crossing switches (Doppelte Kreusings Weichen, DB 1981, 55; DR 1971, 119), and are considered in Chapter 31.
This bifurcated view of graphic signals is undergirded by the character of the signal itself: all-lighted graphic signals are stationary signals: all possible signal combinations are present on a single face. By contrast the partially-lighted graphics are revolving signals. The revolving character eliminates the need to obscure some dimensions of the message indication cycle since only one signal face is present at a time.
Possible shapes for graphic (partially-lighted) include rectangles, circles, parts of circles and a plethora of arrows. Arrows can range from representational forms to decidely abstract varieties. Circles are both full and partial; the partial forms bear a resemblance to slivers of the moon. Another version of this signal (though for non-switching functions) consists of a circle with a movable bar that resembles the positions of a semaphore signal. The housing for a graphic indicator is frequently square in shape for the circle or arrow messages; the other face of the signal is an upright rectangle. The graphic follows the rectangular shape. Chapter 32E2 describes the message significance of the graphic forms.
What has been said of graphic signals can be said of alphanumeric signals though more hesitantly. Day messages are possible but it would appear that these messages are normally of a lighted character. Therefore they will be considered under that heading. This view can be contested: many systems employ route and junction indicators and some unlighted versions can not be altogether ruled out.
A final form of the graphic and geometric area of signals is that of the track indicator (also known by several other names; see Glossary). This signal is very much obsolescent (possibly only the Southern Pacific in the U.S., and the Australian National Railway employ it to any extent; NZR has a variant form: see below). Even though it may be largely of the past it is important to include it in the study because of the range of symbols and messages that it contributes to transportation markings (This coverage is an amalgamation of information from several references including Hall Signal 1913, 60-F-a & 60-H-a; US&S 1911 & 1929; Southern Pacific, 141, 142; Sante Fe 1909; Union Pacific [CCOR 1967, 130, 131]; Rock Island ["Electric Lights", 1936, 627, 628, 629]; and ANR 1947, 139) .
It may be debated whether it is a graphic-shaped or a geometric-shaped signal. Since many of its forms display graphic designs it seems more reasonable to place it with graphic signals. Many of the track indicators are unlighted though some partially-lighted forms (and possibly fully-lighted though of a marginal nature) are extant.
The several major forms center on the word miniature: whether semaphores, pointers, positions, discs or lights. Some forms emulate a full-sized form; other forms are exclusively track indicators; all are small. The semaphore types can be either UQ and LQ and are two-position; pointers are three position. The position form, formed by rows of dots, exhibits one of two messages contrary to position-light signals. The disc indicator is perhaps the only remaining version of the formerly important disc signal in the U.S. The pointer does not have a full-sized version.
The different names may be "only semantics" though the names may indicate differences of substance. The switch lock indicator, for example, may constitute a variant form though symbols and operations closely resemble some members of the track indicator group (ANR 1947, 139; NZR 1979, 115).
Messages for Geometric and Graphic Signals
Messages for graphic and geometric signals constitute a varied and complex situation. There is more diversity and less centralized regulations than for many other signals. This segment can only offer a general survey of these messages though an attempt has been made to offer some specifics within a context of synthesis; reference to individual signal codes is necessary for detailed information.
Messages for graphic and geometric signals are considered in this order: revolving discs, rotating discs, revolving panels, geometric signals (day and night functions can be separate), graphic signals (day and night can be separate), graphic signals (day and night are integral). Graphic, geometric and alphanumeric signals which are all-lighted are reviewed in Chapter 31.
Geometric Signals: Rotating and Revolving Discs and Panels
Many, perhaps all, of the revolving disc signals are U.K. and U.K.-derived/influenced markings. Despite the restricted range of functions for these signals they represent a complex situation. The "face" with the stop indication is usually a white disc with a red bar (horizontal) or a solid red disc (see for example, WAGR, 486-487). The lamp is usually red though a limited number have purple (for example, VR-A, 28; ANR 1947, 113). The "face" with the proceed message offers more variation. In some instances this side is a "blind side" indicating proceed by a lack of a specific message (which can suggest some signal boards, and U.S. style targets. In other instances a band is added to the housing to indicate proceed while in yet other instances a white disc with red (but slightly smaller than that of the stop side) is present.
Colors for proceed indications are green or white; white possibly representing the proceed color at an earlier time, or as a substitute for green of mainline indications. Other less common formulations are solid green and solid white discs (both in Pakistan,
PR GR.S. 5). Colors at night include red for stop indications and white or green for proceed indication. U.K. has one - now obsolete - solid red disc with an upright green rectangle (U.K. K&W 1963, 51).
These signals serve as points/switch indicators and as shunting signals. There is no clear differentiation between shunting and points/switch signals. Though it would appear that these revolving signals are more often employed for points indicators than for shunting purposes. Appendix I offers a summary of specific uses for the signals according to the individual systems.
Rotating disc signals are found largely with those systems employing revolving disc signals. ANR offers a rotating signal though no revolving models (ANR 1947, 113) . Not infrequently the two forms of discs include considerable usage of white discs with red horizontal bars. The variant forms include full discs with signal lamps, full-disc with flood-lights, partial disc with signal lamps, and the glass-enclosed signal with arm or bar.
The white disc with red indicates stop if the bar is horizontal and proceed if at a diagonal position. Lights are red and green for two positions and red/green/yellow for three-positions. These colors bear the standard meanings. In some instances green is explicitly stated to be a clear but slow indication (ANR 1947, 113) .
In the case of ANR, purple indicates stop for a "platform starting signal" (ANR 1947). Red for ANR indicates a shunting signal. A review of signal codes including the rotating disc signal indicates that they are primarily used for shunting purposes. A variant form, white disc with yellow bar (U.K. K&W 1963, 23) is a points indicator; a second U.K. variant, the black disc with yellow bar, is a shunting signal.
The full disc without signal lamps - but illuminated by floodlighting - is closely related to the main form of the disc signal with signal lamps. The glass-enclosed signal with arm is included here because it too is a disc signal. The signal has a black arm on a white background. It serves as a repeater signal (a signal repeating the indications of a signal which is difficult to see because of obstructions) in U.K. and as a shunting signal in NSW (U.K. K&W 1963, 23; NSW, section 23) .
Free-standing Geometric Signals and Geometric Signal Messages
The variety of messages and the lack of central code stipulations creates a problem in discussing message indications for open geometric signals. An individual railway (at least in the U.S.) has a broad range of shapes of targets to choose from and perhaps an equal freedom to determine the meaning of the shapes, colors and positions. This range and freedom is counterbalanced by a conservative principle often at work in transportation markings: specific shapes and meanings have often been handed down from generation to generation. So that shapes and meanings found in Victorian times continue to be used by many railways. While this coverage can not provide very much precision in summarizing meanings it can suggest meanings for such indications that will often hold true.
The shapes that these targets or open geometric signals may display runs the gamut of geometric shapes: arrows, prisms, ovals, circles, rectangles, squares, diamonds, lozenges, "masks." And many of these shapes can develop sub-patterns of their own. And target vary from a few inches in height to ten feet or more. Some U.S. sources number targets (Bethlehem steel for one), and railway systems may group all of them under terms such as switch lamps or switch indicators. This compiler has found it necessary to attempt a word description for the forms though that may be arbitrary and perhaps idiosyncratic. Sources for targets include ANR 1947, 136, 137, 138; EFEA 1958, 145; FNC, Ch II, Art 33; FNM, 127-128; PNKA 1971, fold-out; ROSTEJUS 1954, 22; SBB 1981, 22; U.K. and U.K.-influenced systems have targets as a part of disc and other signals though these are not exclusively target indicators.
A special shape found in North America, and ANR is the "mask" shape. This term was coined from the resemblance of the target to face masks (such as Halloween masks). There are a variety of shapes of masks; most have "eyeholes" drilled into the metal though there are also some "eyeless" versions. Arrows represent a relatively common form; arrows, squares, rectangles, and "prisms" (the last-named is a rectangular-shaped stripe of metal with pointed ends mounted diagonally) are other available shapes. Obround-shaped can also be termed lozenge-shaped was coined from the apparent resemblance of some targets to cough drops and similar medications. Since many targets are double-vaned, two different shapes are often found together; arrows and masks are common components of double-vanes. Double-vaned targets with a single shape have sometimes employed but there are drawbacks to one shape for both indications (Camp 1903,
345) .
Messages bear some resemblance to those of semaphore signals. For example, the nineteenth century target of prism and mask suggests a proceed indication by the diagonal position of the prism, and the horizontal postion of the mask vaguely suggests a stop message. This specific target is in use in the U.S. and ANR and bears these messages (Bethlehem 1981; ANR 1947, 172). The message of proceed is seen from the perspective of the mainline and also the message of stop. A target with one vane and a blind edge suggests a European signal board in that the non-message or blind-edge indicates proceed. Arrows and "fish-tails" can indicate the "side toward which the switch is thrown" (Camp 1903, 346) .
Colors, day and night, are in harmony with those of mainline signal usage. There are instances in which white is a clear color (ANR for example; ANR 1947, 137) and it is conceivable that this dates back to the time when white was the clear indication not green. This is also true of the Philippines where white discs are employed for mainline though red lamps are in use at night (ROSTEJUS 1954, 22). White can also provide an alternative of green in mainline situations. Clear, green, and red meanings are from the viewpoint of the mainline with the opposite meanings from the siding or other divergent line. Purple is sometimes found with derail situations (again ANR); purple is also in use in Japan (JNR, 2-8) .
Messages for various forms of disc signals are complex because of the variety of forms even though many of those signals are only found in a few systems; the extensive coverage may belie the limited usage of those signals. Graphic signals present the reverse situation: many signals which can be briefly summed up.
Graphic signals generally use simple forms: rectangles, arrows, circles and partial circles. Within these forms the specific design may show variation: an arrow can be very representational; it can also be an abstract form. But all forms of arrows can be subsumed under the heading of arrows. The Germanic mode of signals for points is a common form of those signals. Many of these graphic signals are found in European systems.
In nearly all instances the signal housing of these signals is black and the shape of the message indication is cut into the housing walls. The signal lamp, when in operation, is seen through translucent white glass. White on black provides a clear contrast and the resulting message is unambiguous. As noted earlier with graphic signals, single forms can be seen when unlighted; double-crossings (such as in Germanic systems) can not be seen and therefore are included with all-lighted graphic signals.
Basic messages for graphic signals include an upright rectangle for a straight route for a train. Arrows indicate right or left. Circle indicates route set for mainline usage. Partial-circles indicates route set for a divergent line. The variant classification (Ch 2 9B) provides illustrations of the basic forms and also variant forms of graphic signals.
Messages for track indicators follow a simple pattern: track occupied or track not occupied. While the means of displaying that message can vary the actual message does not. Semaphore indicators present standard indications though the message is couched in terms of occupied or not occupied rather proceed and stop (This segment is based on an amalgamation of several sources treating of track indicators: Southern Pacific, Sante Fe, ANR, Rock Island, Union Pacific, US&S 1911, 192 9, Hall Signal). The position form consists of several dots in a vertical plane for not occupied and the same number of dots in a horizontal line for occupied. There are two lighted versions: one that is turned on when the track is occupied but dark otherwise, and the second that has standard green and red indications. Due to its limited power it may be asked whether this is a fully lighted or a partially-lighted form.
The pointer type has three indications: the pointer, when positioned to the right of center (green panel), indicates one of four messages all of which denote no danger; the indicator, when positioned to the left of center (red panel), indicates one of four messages all of which denote danger; when the pointer is positioned in the center (the word train is provided in place of a color such as yellow) it indicates "train is approaching" and appears to constitute a cautionary message. Three-position indicators were employed on double tracks at main line switches. The disc form displays a red disc for any of four messages; all of which denote danger; the withdrawal indication denotes one of four messages all of which signify clear. ANR has a variant form that partially resembles a semaphore arm but also bears resemblance to a check mark (ANR 1947, 139). NZR form has a bar-shaped symbol that is referred to as an arm. NZR provides a dual means of portraying the message: illumination or lack of it can substitute or supplement the arm (NZR 1979, 115) .
