An alien twist on the On/Off Switch symbol

My post about the evolution of the On/Off Switch symbol turned out to be very popular with this blog’s esteemed readers. So, here is a second serving on the subject. This time, something completely different…

Switch on Alaris pump controller

I was visiting someone in a hospital and I saw this piece of medical equipment by Alaris Medical Systems. From what I could gather, it was a controller for a volumetric injection pump that was administering medication to the patient at a programmable rate.

So – look at the symbols around the big key-switch (sorry about the quality of the hurried cellphone photo). Obviously, they’re meant to be conventional icons denoting some functionality – maybe On, Off, and something in between? Or Fast flow, Slow flow, and Manual flow control? The point is that it’s clear that they do mean some three states, and that their distinct simplified forms map to those three meanings somehow, yet for me, as a non-medical person, they could just as easily mean glrrrph, drerp and hoomphla. I’ve completely failed to decipher this symbolism. If you know what it means, add a comment for the benefit of the rest of us.

I assume the nurses that use this gear have been trained in its use… still, one wishes they’d add the meaning in plain English alongside (or instead of) the mysterious icons. But then, that goes to “one word can be worth a thousand pictures”, as I’ve considered here.

Which reminds me of a question I’ve pondered in some idle moments: would an alien visitor make any sense of our ubiquitous arrow symbol? Or do you have to descend from a specific hunter-gatherer background to feel that it must mean motion in the direction of the arrow’s tip?…

3 Responses to “An alien twist on the On/Off Switch symbol”


  1. 1 Frank

    Well Nathan, from your photo it would appear to be an Alaris PCAM Syringe Driver. My first question is: Why do you, an uninformed member of the public, wish for the operational indicators to be labelled in plain English? Are you intending to operate the device yourself anytime soon? Is it just so that it can satisfy your curiosity as to what each of the different settings does? In that case it’s a good job the settings are locked out with a key, to prevent people’s curiousity getting the better of them!

    Perhaps I’m being too harsh, so I’ll enlighten you as to the intended meaning of each symbol. The top position (dot outside the circle) turns the power off. The next position (dot on the edge of the circle [hence neither on or off]) is the “set” position – used to select or modify protocols and to access configuration and test routines. The final position (dot inside the circle) is the “run” position – used to start the infusion. And yes, this is clear to anyone using the equipment as they will have been fully trained in its use before they are allowed anywhere near it, otherwise it would leave the operator, manufacturer and employers wide open to lawsuits in the event of incidents.

    If you want a power symbol combination to be truely perplexed by however, I would direct you to the Siemens Cios Fusion mobile Image Intensifier. It has 2 power buttons – one off, one on; one with a dot outside a circle and one with a dot inside the circle. Seems straightforward enough, except when the power is on, the OFF button is illuminated! Can you think of another example where the OFF button lights up when the power is on?

  2. 2 Nathan Zeldes

    Thanks, Frank, for this informative explanation! Perhaps we engineers are really too inquisitive…

  1. 1 And another On/Off power switch symbol! at Commonsense Design

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