Background information:
Electronically operated indicators on the platforms, which indicate when and where to, the next train leaves from the platform in question.
CTA is an abbreviation for Central Train Pointer. Electronically / mechanically functioning indicators on the platforms, which indicate what time and where the next train leaves from the platform in question. The CTA's were introduced in the 1970s, mostly still in test versions and at different stations just slightly different from each other. In the 1980s, the most commonly used model went into circulation. Uniformation also became a fact. The blue areas with track number were always closest to the track in question. The white areas with text indications therefore always hung more to the centerline of the platform. These CTA boxes, with folding roll system, were replaced around 2010 for TFT screens. Tip for the detailers among us: Buy two different sets of T pole CTA's and exchange the stickers to ensure that the CTAs indicate a different track number and final destination on both tracks.