I saw this series of 4 circles in the schematic of an Arduino board. Similar circles appear in other Arduino schematics, though I don't think they are Arduino specific (which is why I post here rather than on the Arduino forum).
What do they mean?
Electronic – What does the series of circles in a schematic mean
schematicssymbol [~]
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I'll take a guess though I don't know for sure. The key words here are publication quality and professor. LaTex does a very nice job when used in conjuction with CircuitTikZ. LaTex is very much used for typesetting documents in the university setting.
It's a flexible connection of some kind. In this drawing, it is likely to represent a trailing or reeling cable (I will explain this a bit more below.)
Supporting my claim - from AS1102.3 Graphical symbols for electrotechnical documentation - Part 103: Conductors and connecting devices, we have:
Note AS1102 is based on IEC 617 Graphical symbols for diagrams.
Contrast the symbol for a jumper ("connecting link"), also from AS1102.3, and a fuse, from AS1102.7.
What's a trailing cable?
A trailing or reeling cable is used to power mobile equipment, i.e. a mobile drilling rig, or mobile substation.
In this application, I think the 'sub-sea' transformer is in some kind of waterproof container, connected to the surface supply by trailing cables. Flexibility is required for the transformer to be moved around, or to move with the water currents.
Note that trailing cables are a special breed, not like regular cables. See Olex catalogue for trailing and reeling cables. Generally these cables are much more flexible than normal cables, are designed to withstand cars running over them, etc. There are also special protection features to detect if the cable has been damaged - these aren't required for normal cables which spend most of their life living in a protected environment, i.e. conduits.
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Best Answer
OK, I found an Eagle schematic file of this, and I checked the properties, like jwsc suggested. They seem to represent fiducials.
Comment: fiducials don't belong on a schematic, they're purely PCB-related. You don't place mounting holes on a schematic either. When they appear on a schematic they will most likely show up in the BOM as well.