An upper quadrant automatic semaphore mounted on a 30ft post. The signal can take 3 positions over the upper quadrant: horizontal (STOP), 45 degrees (CAUTION) and vertical (PROCEED).
Home and distant 2-position automatic semaphore signals appeared in NSW in the 1900s. Later (1920s?) a 3-position variant for use in areas with higher traffic densities started to appear. These were double-light semaphore signals where the lower light had a red/green spectacle arm in place of a distant semaphore. The semaphore had 3 positions but the 3 spectacles showed only 2 colours (red, green, green). By day, CAUTION was indicated by the semaphore at 45 degrees, while at night the light indication was green over red.
In the 1940s the 3-position single-light automatic signal started to appear both in new installations and in conversions of double-light semaphores. The middle spectacle was changed from green to yellow (red, yellow, green). The single-light signals still had a lower light, but only as a backup in case the semaphore's lamp extinguished.
A peculiar feature of these automatic semaphore signals was the use of oil lamps despite electric power being available for the signal-arm motors. In images taken in the 1950s, oil lamps mounted on signals installed in the 1940s can be seen. The use of oil lamps may be the result of bargaining with the railway unions about the introduction and updating of automatic signals. Another consideration could have been the reliability of electricity supplies in the first half of the 20th century, although local battery backup could have largely overcome this risk.
Each signal was controlled by a nearby relay hut ('NSWGR automatic signal relay hut', kuid:368725:20070) in which track-circuit detections were converted into signal-motor instructions to set the semaphore position. The spectacle arm of the lower light was driven from a jointed rod that connected it to the semaphore. The complex movement of this rod is beyond my skill to animate, so it has been omitted from the model.
The signal has a black name board mounted on the pole with white characters aligned vertically. This board can be populated by the user via the Properties editor in Surveyor mode. Actual names used for these signals followed the format <single alphabetic line code (optional)><distance from Sydney Central to the first decimal place>. Line codes were only used in the Sydney and Newcastle(?) suburban networks where there was parallel running of different lines.
Тип: Сигнал