Diagram callouts, take II

[Geoff Hart <Geoff-H -at- MTL -dot- FERIC -dot- CA>]

Christi Carew provided additional information: <<In a nut shell, order
matters. There are labels, but (1) they vary for each
user depending on their specific panel, and (2) there are actually many
different possible places that users might connect to on the panel, and I'm
just illustrating the general connection process.>>

If that's the case, then numbers or letters are likely to be misleading. If
I'm understanding this right, it's like having a series of stereo
amplifiers, each of which has input and output jacks but with the jacks in
different places. If that's the case, using letters or numbers could be
quite misleading, because a user in a hurry (or a tired user or an
inexperienced user or...) is likely to use the positional clues (the
location of the label) rather than the functional clue (what each connector
does) to make a connection. On that basis, you should probably get away from
simplistic labels entirely and use descriptive labels: "connect the red
cable to the input jack" or "insert your bank card in the slot with the card
icon above it, not in the slot with the envelope icon".

<<given the technology, the connections have to be done very particularly.
Some plugs have to be done simulateously (e.g., plug in A and B at the same
time).>>

I have this image of two crewcut men in a bunker, holding large keys, and
staring at each other with sweat trickling down their foreheads while Dr.
Strangelove looks on approvingly. <g>

<<I think what Janet said above about users needing to pause just a moment
to find the right next letter is a good
point. If the users do it out of order, bad things can happen.>>

See previous image. <g> If you want them to pause a moment to think about
what they're doing, use full words, not letters or numbers; letters or
numbers are much easier to misread, and don't match what's going on in the
user's head. Think of it this way: When users are thinking about what comes
next, they are using words to describe it to themselves, not one-character
labels, so the labels should relate as closely to those verbal descriptions
as possible to provide a clue about what that next step is: in effect, if
they're thinking "insert key and turn it clockwise to start the car", say
so; don't say "step A followed by step B".

--Geoff Hart, Pointe-Claire, Quebec
geoff-h -at- mtl -dot- feric -dot- ca 
"The paperless office will arrive when the paperless toilet
arrives."--Matthew Stevens