Morning all!

I wouldn't want to withhold this little overview for which I took a couple of photos during my shift yesterday, illustrating possible means for how engineering works on tram lines may be safeguarded while keeping traffic flowing.

At present, the Landsberger Straße terminus at the north end of Line 4 is undergoing refurbishment, to which end various temporary signalling measures for road and rail have been put in place. This is made doubly interesting by the fact that this terminus is located at the end of a short stretch of single track, so right now, there are two different but related elements of signalling to be observed.

But, let me regale you with a couple of "general" images first . I spent the first couple of hours on Turn 421, booked with…

…1346 "Thonberg" and 1330 "Wiederitzsch", seen here at the arrival point in Stötteritz…

…and halfway through the loop as the boarding point was still occupied by the turn ahead of me. Due to the construction work at Landsberger Straße, we have a fairly generous turnaround of 19 minutes at Stötteritz during daytime, and seven at Landsberger Straße, owing to an additional turn having been booked on the line for relief.

Here, I am stood at Landsberger Straße, where, while engineering work is ongoing, the arrival point has been temporarily relocated immediately ahead of the departure point.

The construction site has been outfitted with a temporary signalling arrangement. However, travelling up to Landsberger Straße, the first important piece of signalling you encounter is at Beyerleinstraße.

As I said, the final stretch of route from Beyerleinstraße to the terminus is single-tracked and safeguarded by a Single Track Signalling suite, which I suppose could be a suitable English interpretation of the German term, "Fahrsignalanlage", or "FSA."

The STS suites we use utilise either pantograph head detectors on the OHLE for a route request, or key lock switches – the latter being standard at those termini located at the ends of single-tracked sections. On single track sections on the open line, pan head detectors are used for greater convenience, though these signalling suites can also be equipped with key locks to serve as a backup means of route request.

At Beyerleinstraße, pan head detectors are used for outbound services. The STS screen here shows "Stop" and "Acknowledgment of Route Request."

Later, the screen also showed the letter "F", which is an indication that the road and pedestrian traffic lights co-located with this STS unit have been shut down, as is normal here in the early mornings and in the evenings.

As indicated, the present arrangement at Landsberger Straße requires two important signalling components to be kept in mind simultaneously! First of all, there is the STS suite, which the signal screen suspended from the OHLE is part of. The route request key lock is off image to the right.

And there is this temporary signal interlocked with the temporary road traffic lights on the outbound lane, set to a fixed timing pattern. You may depart only if, one, you have a clear STS aspect, and, two, if the temp signal is unlit, as in this case.

Here, the temp signal shows "Stop", and changes to the combined aspect of "Stop" and "Await Clear" (the "dot" aspect, set in the lower of the two chambers in this case) immediately prior to turning dark to indicate "Clear."

And there is the temporary set of traffic lights that has been set ahead of the terminus.

Also take note of this automatic swing-away barrier, which is enabled by approaching trams.

And to round everything off, two nocturnal photos…

…of my NGT6 tract prior to depot return, signed as Line 4E for the stretch to Central Station, and there re-signing itself as Line E for Sportforum.

And for my second half on Turn 414, I got 1124 "Marianne von Ziegler".

Thank you for reading and do feel free to ask any questions you might have!