[landr0id]

>so a customer without a smartphone could relay the diagnostic session to a technician

Do you mean by mimicking the noises themselves?

[wpm]

No you see you just need to buy specially marked boxes of Cap'n Crunch that have a plastic whistle in them that plays the tones for you.

[userbinator]

I wonder how many HN readers still get that reference (and 2600, etc.)

[Y_Y]

I'm merely middle aged, but I've read the hacker lore.

https://en.wikipedia.org/wiki/Blue_box

[hunter2_]

We make use of a service already existing without paying for what could be dirt-cheap if it wasn't run by profiteering gluttons...

[notpushkin]

By holding their phone up to the machine.