My wife and I live in Switzerland and are members of Dignitas, with an eye to potentially using their services if it ever came to that. Meanwhile we support their activities because we believe in their mission and how they approach it.
They counsel you, the client, from the start and try to steer you toward a hoped for objective of *not* offing yourself; but then, if they feel you are certain and two different doctors have signed off after examinations, they will come to your home (or hotel room, I think) and set up the apparatus for introduction to your system a lethal drug that your doctor has prescribed for you.
However, they are very strict on one thing: only the person who is the client may activate the drug flow. Otherwise, it's murder instead of suicide. Your family or close friends can help in all other ways except this crucial one, as far as I understand.
The Swiss government got a bit antsy about the previous single doctor rule and doubled it as a precaution. After the death, Dignitas stays with the body and notifies the police and signs the statement about what happened. They can also handle the, erm,...disposition of your mortal coil, per your wishes.
We came home from a holiday out of town last year to find that our upstairs neighbor used Dignitas while we were away. It was very sad to learn about her demise, but we were glad that she had the option.
When my wife's father, in the US, was very ill with dementia we had a visit with him from his gerontologist who said, "We doctors are very good at keeping organs alive; but sometimes to the detriment of the whole person." He asked FIL if he wanted to die with dignity or via heroic measures that would be painful and drawn out, and where the end would be the same. FIL chose the former and when, later that year, his condition really deteriorated and he felt he couldn't go on anymore, he just stopped eating and drinking, refused medication, and was gone in three days. He was a brilliant university professor of electrical engineering (who invented satellite telephony), who bowed out with as much dignity as he was able to command. We felt glad for that, at least; but recognized FIL's luck in getting an exceptionally understanding physician.
Here is the Dignitas link in English:
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