Trev,
To quote from the maintenance manual:
"The collective friction unit is located below the collective stick assembly under the cockpit floor panel. [It] is an electrically operated series of drum wrap springs that provide friction to a set of drums. The first series maintains friction at the 5 pound resistance level when the pilot releases the friction. The second series applies 25 pounds of resistance when the pilot engages friction. The collective friction unit is linked to the collective stick assembly by the collective friction link.
The collective friction release switch allows the pilot to turn off friction by moving the switch forward or momentarily release the friction by moving the switch aft. The momentary release position is spring-loaded to return to the centre or on position."
In other words, imagine the friction switch as a three-position rocker switch spring-loaded to the centre position and operated by the first two fingers of your left hand under the collective. If you want to apply friction (ie 25 lb resistance), you squeeze the switch backwards, adjust the collective position, then release the switch. If you want to release the friction (ie 5 lb resistance), briefly rock the switch forwards.
In practice it's not perfect; the Tq will tend to drop slightly from the point at which you set it, so I usually pull slightly more power than I want (by about 3-4%) and let it settle. It's certainly a very strange system that initially takes some getting used to but, like most things, becomes second nature after a while.
E99