The device with which the cosmetic surgery is conducted is delightfully called the Aesculaptor Mark III. Doc brags that it is “the latest. It’s completely self-contained.”
In it, the patient lies flat in a recess on a rounded table, the tilt and orientation of which is computer controlled. Above the table is a metallic sphere with six spidery articulated arms. Some of these house laser scalpels and some of these house healing sprays. The whole mechanism is contained in a cylinder of glass.
To control the system, Doc has a panel made up of unlabeled buttons and dials, a single blue monitor, and another panel displaying a random five-digit number and two levers. One is labeled “ANODYNE” and the other is labeled “KINESIS.”
When Doc receives a mysterious call (on what may be the earliest wireless telephone in mainstream science fiction,) he receives instructions to murder Logan. To do so he turns off the healing by moving the ANODYNE lever into the lower position.
So. Yeah. Also just terrible. I mean there’s the plot question. I ordinarily don’t drop into questions of plot, but come on. If Doc wanted to eliminate Logan, wouldn’t he increase the anodyne, so Logan wouldn’t know he was being killed until it was too late? If you wanted to torture him, wouldn’t you put him under a paralytic first, and only then turn off the anodyne? Turning on the KINESIS (moving lasters?) and turning off the anodyne just seem counter to his actual goals. Unless you want to fantheory this so that Doc’s instruction was "make him escape."
But yes, back to the interface. There’s almost nowhere to start. Undifferentiated controls? Unlabeled controls? No visual hierarchy? Only the device itself and an oscilloscope to monitor the system and the patient’s trending state? Un-safeguarded knife switches for the primary controls? And note that the fail state is in the direction of gravity. If that knife switch gets loose, oops, you’re screwed.
Logan’s Run took place long before the lessons of the Therac-25, with its tragic interface and programming problems that resulted in the deaths of several cancer patients, but even audiences in 1976 would not believe that any medical device would have such an easy means of disabling the only aspect of it that keeps it from becoming an abattoir.