I'm talking about powers like pain resistance, Mystic armor, and Improved reflexes, and Improved Physical Attribute...

If you thought of them as "powers" like super powers then yes. But if you think of them as just part of the adept then no. It would be like trying to just turn off your hearing IMHO.

As far as canon goes, I don't know.

As far as role-playing the situation goes, it would depend on whether or not the adept knew he was an adept. (Some people like to play adepts who are unaware.) If he knows, then he ought to be able to suppress his powers; knowledge implies control. If he doesn't know, then of course not; ignorance implies lack of control.

I know I can hear.

I interpreted the rules/examples given for mana warps in MitS to mean that powers are activated just like cyberware.

I've always played it that they can be turned off as a free action and on as a simple.

Good suggestion, WR. I'll start using that one.

I think it would depend on the Power irself. Things like Improved Attributes and Magic Resistance shouldn't be able to be switched off at will, whereas other Powers would be.

Well the adepts get to pick and choose which selection of powers they use when the combined cost exceeds their magic rating, so we always just went with it being a free action to turn them on and off. :o/

Lilt: If you've got nothing to say, how about you say it in normal sized text? That large is just annoying. Thank you.

I'd go so far as to say that any adept can choose to adapt (hah!) any level-based power to any chosen lower level. But I like the image of the adept having to concentrate (cloes his eyes and go "ommmmm" for a moment) to regain the maximum potential; Hence WhiteRabbits "simple-action"-option.
The adept weren't born with the powers but acquired them one at a time through rigorous training. IMO they are 'supernatural skills'.

If you cannot turn them off, why is there a maximum number of powers you can have on at once, regardless of how many you actually know?

Eg, an adept who's lost a point of magic doesn't lose the powers, they lose the ability to have them up at the same time as all their other powers (unless they geas).

in one of the novels there's a very good depiction of a physad, who follwos coyote. Whenever he wants a power, he makes a short prayer, and visualises the 'wheel of life'. His totem then grants which ever power it is.

And what about killing hands? If its on permanently you have problems...

I'd definately rule that powers can be activated and de-activated. Otherwise I'd never be able to catch the bastards unawares...

Isn't there a FAQ entry on killing hands which states that to use it at a lower level you need to increase TN (as per the rules on pulling punches)?

Sensory stuff should be able to switch on and off if it interferes with normal senses or provides a penalty (bypass thermo-smoke for instance).

Basically, just treat it all like the cyber equivalent...