Schattenbahnhof

So, what's a "Schattenbahnhof" ? Literally translated to English it means "shadow station". The more common linguistic definition is a "hidden yard". This is mostly a yard that it used to "store" trains in a hidden area of the layout, so you can surprise yourself and visitors with many trains entering and leaving the layout while operating. You can basically have 2 kinds of hidden yards, "storage yards" where trains are "parked" on hidden sidings with a single entry and leaving point per track, or a "pass-through" hidden station with the entrance in one end of the complex and the exit at the other end of it. What we mean by "Schattenbahnhof" here is the pass-through type.

The actual wiring is not shown here, but we hope you will understand how to do it with the help of the operation principle scheme presented here. This article is contributed by Lars Westerlind.

The idea

Here is a "shadow station", shown as an example with four tracks. The coupling automatically chooses a free track, or stops before if it's full, including optional block control before the station. Starting of the trains is controlled manually by setting U1-Ux to green.

The schema is secure, except if several tracks are put to green at the same time. Feedback of the position of U1-Un is recommended to avoid that and for convenience. Feedback is got by using catenary connection of U0-Un, or using relays with end shutoff contacts.

The Ux relays may be of Märklin 7245 type at least. They are all controlling trains, and there aren't connections left for showing green/red; who cares in the tunnel.

The scenario

The trains enter in the hidden upper right corner of the illustration, and leave the hidden yard at the bottom left of the illustration. During the travel from upper right to the lower left, a train crosses 3 stop track sections (S, h0 and hx (x=1-4), and triggers 5 indicators (e, ax, bx, c and d). For this scenario you need five 7245 relays, 11 momentary contacts (momentary contact tracks or reed sensors) and 3 turnouts.

Some symbol explanations:

S	Stop track (Signal) before the hidden station, in case all tracks are occupied
h0-h4	Stop tracks
ax, bx, c, d, e	Momentary indicators, x=1-4
W1-W3	Turnouts (switches), can be g (straight) or r (curve)
U0-U4	Universal relays, can have the states g or r

Event	Action	Comment
a1	U1r	When contact a1 is triggered, relay U1 is set to r, stop track h1 set to "red" (stop).
a2	U2r	As above, but for U2/h2.
a3	U3r	As above, but for U3/h3
a4	U4r	As above, but for U4/h4
b1,b2,b3,b4	G0, Sg	Either of these contacts set the turnouts, or U0 to red if the station is full. The block signal is set to "green" (go). The switches are set through a logic connection path, where all Ux settings decide what turnouts should be set.
c	R0	When contact c is activated, nothing happens except if the station was full. In this case, the switches are activated at this place instead of at bx. The purpose of U0 is to prevent connection between bx and c, as the signal S should not be activated by c.
d	U0g	When contact d is activated, stop track h0 is set to "green" (go)
e	Sr, prior block g	Normal block control. There is at least one free track in the area since the contact e was triggered.

Connections

The idea is that each relay U1-Un is green if the corresponding track is free, and red if there is a train. U0 is red only when all tracks are occupied.

Normally bx sets the turnouts to a free track, and sets' prior block signals to green. Only when the station is full, U0 is set to red, again letting prior block signals start their trains.

When a train exits nothing really happens, except if the the station was full. In this case, the turnouts are set to the now free track, and U0 is set to green to allow a new train to enter the hidden station.