One of the most important components of the interval graphics are the clocked lines. Its essential properties are already included in the name.

1. Clock: trains of a clocked line drive clocked, that means they are summarized in a clocked group.

In FBS, "clocked trains" can be grouped into clock groups. This can happen by "copying train in intervals" and selecting the appropriate option or by creating a clock group afterwards. A clock group then symbolizes a clock. Thus, these clock groups are used in the interval graphics of the program to recognize clocks or clock lines. This means that the clock lines arise always from the clock groups defined in the graphic timetable.

2. Line: trains of a clocked line are part of a line, that means they have a line name

The second requirement is fulfilled by the fact that trains of a clocked line have a line name. The assignment can be made in the train data window for each train individually or via the multiple selection for several trains at the same time. Trains of the same clocked line should have the same line name.

In order for the clocked lines to be listed in the selection window, both prerequisites must be fulfilled, that is to say, there must be both clock groups and the trains in the clock group must have a line name.

If one or both of the prerequisites cannot be fulfilled, there is still the possibility to create a clock line from "individual trains". To do this, you first have to right-click and select "all travel trains" in the selection window of the clock lines. Now you can select the train for the go or return direction, which should serve as the data base for the clock line.

Note that only one or two trains form the data basis for the clocked line. If, after the creation, e.g. the train number of these trains is changed, or the trains are deleted, the data base of the clocked line is lost. When creating clocked lines based on clocks, this happens usually very rarely, since a clock group alone consists of at least two trains.