I have used the Qlink pendant, and have detected significant positive benefits from doing so. I am not sure it actually "tranqulizes the mind". It is supposed to protect one from radiation from computers and other electrical devices, and also from wireless radiation from cell phones and microwave antennas, which bombards one's body invisibly and constantly all the time. It is also supposed to balance one's biofield, which is the invisible envelope of energy that surrounds each of us, by establishing a resonance between itself and the biofield.
What gives the technology a lot of credibility to me, is that the inventors and researchers involved in developing this technology include people such as Dr William Tiller, who is one of the top Material Science professors from Stanford University. He has written a few books about Quantum Physics and Material Science.
I tried to be as objective as I could when evaluating the pendant, and found that it does make a significant difference in areas such as increased energy and endurance when exercising high intensity workouts at the gym. I did not wear the pendant for a few days, and found that I was severely exhausted at the gym, compared to when I had it on. There are probably other benefits such as increased concentration and emotional balance, which I am not actively aware of.
The company recently released QLink pendants using the next generation technology (SRT3 or sympathetic resonance technology version 3). I have actually ordered a pendant using this technology, and am eagerly looking forward to trying it out!
