In the beginning, Cameron tells Ruth that he can't think with all the voices in his head. Later when Ruth takes Cameron for psychic training, Ruth says that telepathy isn't about reading minds, but connecting with nervous systems. So is Cameron the only one who can hear voices?
And if scanners can hear the thoughts of other people, how is it possible that all of those scanners in that apartment are just sitting ducks and don't sense two guys storming their room with shotguns? I've seen it twice because I thought maybe I missed something, but nope. More questions than answers on the 2nd viewing...
Well, at the beginning of the film, Cameron was totally untrained. He didn't even know he was a scanner. It took Ruth to train him how to focus his scanner mind properly.
Remember in the old film about Revok, he suffered from the same problems, hearing voices. Revok ended up drilling a hole in his head as a result, to try to let them out.
It wasn't until they were given Ephemerol, the same drug that created them, that the scanning stopped while the drug was in effect.
Once Cameron, and Revok years before him, had been trained by Ruth to focus his scanning, he no longer needed Ephemerol to calm him down. He was no longer uncontrollably scanning others.
The other scanners had already been trained to focus their minds. In fact, that's what they were doing in that apartment, focusing their minds collectively and jointly with and on each other. They were quite literally lost in thought, or scan. They wouldn't have noticed the assassins coming in the room.
I agree with you except for the point about them not needing ephemerol. I did not get the impression that scanners could maintain their sanity without ephemerol. At least not cameron and revok, who had been prototype scannerbabies and considerably more powerful. Cameran continues to get packages of ephemerol in the mail after his training by dr. ruth. Ben, the artist-scanner, maintained his sanity by remote isolation and "rehabilitation through art". His art broker/manager/whatever said he NEVER meets his public.