This page was drafted for BAHN 3.56 beta, before the online HELP information became available. Priority will now be given to the translated HELP information, so please refer to that for the most accurate details.
The general instructions for building are now found in the main writeup.
Signal systems are for securing track sections against collisions and congestion, and for controlling level-crossings (grade crossings). They would be used for example on track sections that may only be occupied by one train at a time, such as single-track sections, turning wyes, block sections or some depot entrances.
The signals can be driven automatically by the trains, as for tram working or automatic block-section working. Alternatively they can be operated on a time basis, or both methods can be used together.
A signal system consists of at least one signal, but usually there are several elements (at most, 255).
Each signal system has a counter.
When an ON-contact ("+"-contact or signal with ON-contact effect)
is passed, the counter is stepped up by one.
When a "-" contact is passed, the counter is stepped down by one.
The count can be done on the basis of trains or
vehicles.
Counting occurs when first contact is made with the signal element,
i.e it is not done with the last axle.
When a time list has been laid down, then the counter will be
stepped at the appropriate points of time.
For each system, there is a threshold value to be defined for the number of trains/vehicles, this is denoted "Max train/car count" in the English resource. When the counter reaches this value, the signals of the system will be set to STOP (red etc.): when the counter falls below this value, the signals of the system will be set to PROCEED (green etc.).
Normal signal systems consist of at least one element with ON-effect, and one "-" contact. If a time list has been defined, which causes appropriate switching, then contacts may be dispensed with. This would also be the case if a signal is only intended to be hand-operated.
The counter can be manually set to 0 or to its maximal value very easily: put the cursor on any element of the signal system and hit F4. If the counter is zero, it's switched to its maximal value: if not, it's switched to 0.
Complex examples of signal usage are shown in Help (in German, natch).
Obviously, when building signal systems you need a way to tell the system which signals and off-contacts belong to each individual system.
For modifying an existing system, you do this by making the system that you want to modify "Inactive". Only one system can be inactive at a given time - this defines the system that you are currently working on.
To make an system inactive, you click on one of its elements and the program will display the situation {Signal system activated} offering you a dialogue to deactivate it (this dialogue can also set/change other parameters of the system). When you are done modifying the system, mouse-click one of its elements (remembering you need to turn your crane into a mouse first ;-) and the program will display {Signal system deactivated} with a button to Activate it.
Or you could completely demolish an system by replacing its elements with plain track or whatever. When the last element of an inactive system is demolished, the system disappears from the program and there is then no system inactive.
To build a completely new signal system, you place its first element, without inactivating any existing system. Program displays {No Signal system inactive} "Create new signal system?" and you answer Yes. When done, you mouse-click on one of its elements and put it into service as before.
Bear in mind that there can be at most one signal system
inactive at a given time, and all signal system work that
is carried out relates to the inactive system.
If you want to get an overview of the elements of the inactive
signal system, then use the Edit/ Search/ Signal-system
dialogue.
The Help menu offers a "List Signal Systems" option.
Since experience shows that errors are common in the construction of single-track sections, it's advisable to run a single test train through a newly-constructed section and verify the correct operation of the signals. If a collision is allowed to take place, the situation can only be retrieved by driving backwards or even erasing the train from the section.
Each signal system has a number, just as is usual in real practice. Each number can only be allocated once. Bahn assigns numbers automatically, but you can alter them if necessary.
Depot entrances can be secured against collisions between entering and leaving trains by combining them with a signal system.
To do this, the number of the signal system is specified in the depot's details (Depot dialogue). For trains that are going on-duty, the depot then acts like a signal with ON-effect, while for trains going off-duty it works like a "-" contact.
Note there may be several trains waiting in on-duty status unseen in the depot. Several depots can be combined with the same signal system.
(The Help information contains a complex graphical example.)
Seems to me the best way to learn how these signals can be used in practice is to load the supplied layouts one by one and scroll around them to see how they have been done. Note that you can mouseclick on any element of the layout and it will tell you what that element is or does. Use ESC to get out of unexpected menus or dialogues. This will also allow you to identify the different kinds of turnout (switches:US/points:GB), so that you know which ones to select when building your tracks.
By the way, if for operational reasons you are forced to "initialise" (i.e de-materialise!) a train that is within a signalling area, the signal would be stuck at Danger. Rescue the situation by re-setting the counter as already shown.
As you have probably noticed by loading the sample networks, trains/trams can follow one another along the line without the need for signal controls (as would be fairly normal in tram operation, but not in real-life train situations). If, on the other hand, trains are liable to meet in opposite directions (on single track sections, turning Wyes etc.) then movements should be controlled by signals; otherwise, a frontal collision is not ruled out.
Here I describe what's implemented, without going into detail about what it might be useful for. Iain Logan has some notes on his web site about ways in which he has found these features useful in practice.
A time-controlled signal system does not need any contacts, although it can have contacts in addition to time control if desired.
When building a signal system, you can take the dialogue "set time data" - you are presented with a panel of times of day. At the times (0-59 minutes) listed at each hour, that system's counter will be changed by one count, in the direction selected by the radio button (upwards, towards stop/red, or downwards, towards proceed/green); and optionally, after the lapse of a specified interval ("Difference") in minutes, the counter will be set back again by one count. When no time difference is used, then you would need to set the counter back again by providing a contact instead.
At each hour the times are listed as whole numbers of minutes
separated by commas, e.g 5,20,35,50 in the obvious
way (of course, the time intervals don't have to be regular
like that).
The procedure for setting the signals to red or green as the count passes the configured threshold value (normally one) is the same as already described. If there are also associated contacts, then these too will be stepping the counter up or down as the case may be according to the passage of trains. Could be fun!
The documentation doesn't actually describe practical ways of exploiting such time controls or with the counter threshold value greater than one. In email the author told me the following.
- This is useful when having a timing-point but some train may be too late. Then use such a signal instead of a timing-point (But be careful with trains running to a depot).
- This is useful at a central node (as Dresden Postplatz or Chemnitz Zentralh.) where some trains will be synchronised by waiting 3 or 5 minutes, especially at night. Maybe you don't have enough room for the timing-points, or you have trouble with the different routes using the same line (and you cannot be sure which train arrives first). In this case you can build signals at all positions BEHIND the node and use a time list which sets the signals RED e.g. 10min before the departure, and the signals will light GREEN after the 10min, exactly at the departure time. During this time the signals will "catch" all trains arriving at the node, and during the rest of the day the signals always are GREEN and don't jam the traffic.
- The method 2. can be made more complicated if you wish all trains should wait for a train which is late. In that case you need counter values more than 1 and you must add contacts in a way that the trains tell their arrival to the signalling system. That's not simple and today I don't know a layout where someone used such a construction, but my brother and me experimented with such systems for saving connections between trains, and these systems worked.
Other things to note are that "*" can be typed into an hour's box to copy the minutes list from the previous hour; and an entire time schedule can be transferred via the clipboard.
BAHN works well also with left-hand running layouts. The stops, platforms etc. can be on the correct side, and additionally in 3.56 a selection of signals, both colour light and semaphore, are available for left-hand running.
Original materials © Copyright 1994 - 2006 by A.J.Flavell