Upon finding the original textbook online and reviewing the wording, my previous answer was incorrect so, I reversed my opinion. Apologies for the Senior's moment.
This is NOT a 3 state switch. The text is incorrect.
There is no active open collector to pull down the bus to 0V < 100 ohms for a logic "0" or even 10k for high Zin.
You answered your own question here:
I would understand if this arrow would point out of the schematic to
show that it is used somewhere else
If you look at the schematic, you can see where it is also used in that snippet, along with some others too:
It is likely there is a backup 12V supply, or the arrow could mean nothing, and it is just there to ...
For true TTL tri-state operation the output must be able to pull up and down. The circuit in your book can only pull up, which is not compatible with TTL logic.
Here is a real tri-state TTL (inverting) buffer:-
simulate this circuit – Schematic created using CircuitLab
When Enable is high Q3 is turned on, which turns off Q5 via D1, and Q4 and Q6 ...
It's a bit tricky, but for single parts/components you can do that. You have to be in the SCH Library. Just go to "SCH List" in the panels.
A new Window should open. You have to change the mode from "View" to "Edit" and change the objects to "non-masked objects" at the top-left corner.
Afterwards, you can change every font, size and color of every ...
Visio seems to work well for me (any before graphics software will do), put the picture of the PCB as a background or layer and draw a schematic on top. You can also have multiple layers and put the to and bottom of the PCB to trace on the same file. You can change the visibility of the layers and trace over both. If you could x Ray inner layers those could ...
No s/w that I know of. However, you could overlay a transparency onto a picture of the board and draw the electronic symbol over the picture of the component, then add the wiring links. All you would have to do then is re-arrange the circuit for readability
This could indicate a twisted pair. I have personally used a similar symbol for that and also some websites agree with this, such as this one
It also looks like SolidWorks Electrical has this symbol for this purpose too:
(the image is taken from this forum)
It doesn't seem to be standardized, so we see many variations.
It's either a Schmitt-trigger inverter or a Schmitt-trigger buffer. It's unclear to me whether the output has a circle or an arrow on it. The hysteresis diagram implies it's an inverter, but that could be wrong.
Edit: as @duskwuff points out, from a functional point of view, it's undoubtedly an inverter. The pin numbers match the SN74LVC1G14 single gate ST ...
It looks like a schmitt trigger inverter like this one (but not this specific one as the pins are different). There should be a Vcc and gnd for this part somewhere else in the schematic.
The question is still open for suggestions. Meanwhile, I've spent some time attempting to rearrange the diagram, and I identified three modifications and the schematic is significantly better now.
1. Increase the Width of the Blocks
Do not put wires directly to the points of connection on the symbol. Use some vertical wires to create additional widths.