What's that got to do with drawing?

The latest round of transport chaos on the GWR line to Paddington was reported here.

A new £16million “bullet” train on a test run caused commuter mayhem after wrecking 500 metres of overhead power cables on the approach to Paddington station.

The major rail hub was almost effectively closed this morning with no services to or from Heathrow and Reading until lunchtime, and knock-on delays expected for the rest of the day....

The incident happened at Hanwell about 10pm last night [HD:16 Oct 2018]. The Italian-built Hitachi train – capable of 140mph - was being used to train Great Western Railway drivers when its pantograph arm, which connects carriages to overhead power cables, got caught in the wires.
Source

It was the last paragraph that – amid a tale of  woe that is by no means unusual – grabbed my attention. At first sight, given the appropriate lexicographical background, the obvious question is '"What's that got to do with drawing?"

At least, that was my response But this is not – as with photograph – a special sort of drawing (in that case, manipulating  chemicals to simulate the process of drawing with light)...

<another_example>
And in digital photography we can see another instance of old technology frozen in metaphor, as discussed here. From graphite to photographic chemicals isn't that big a figurative leap – from one physical medium to another. But with digital photography there is no kind of physical medium (unless you consider that the pixels involved have a physical reality).
</another_example>

... it is a metaphor that refers to a tool that can be used in drawing. If you have a look at this animation you''ll get  the idea.

<process_note subject="flickering lights">
(I originally cut/pasted it into this post, but it made the rest of the post [and also the beginning, though that was not where I was at] impossible to read.

<meta_digression>
Cavemen gazing at a fire are the fore-runners of 20th-century people gazing at TVs (and 21st-century people gazing at smartphones). Flickering light commands attention.

<further_digression>
(Which, incidentally, is where the word focus comes from – a fireplace [source of flickering light.])
</further_digression>

</meta_digression>

</process_note>

You can see where the railway electrification people got their idea; the doofer that electrified trains use to get power from overhead wires is called a pantograph.

The suffix -graph is quite  prolific when it comes to coining words that have nothing to do with drawing. Choreograph, phonograph, tachograph, and telegraph all bear little sense of drawing, and many other -graph words have left the idea of drawing some way behind - epigraph, paragraph, monograph...

But I could do this all day. That's all folks.

b