Re: Several questions. I'm a noob.
First off: Welcome to HERO and the boards!
Second some thoughts. Your Zone of Silence can be built with Hole In The Middle where the hole can be changed with each use. This allows you to cast it will a 1 meter hole or a hole that only allows for the caster to stand in it. You might also want to make it mobile so that it can be moved. If you want it to target a person specifically it needs to be Usable As Attack, but that is not necessary if its mobile.
The thing to remember when dealing with your ideas for making someone more persuasive is that HERO doesn't have a magic resist ability unless you create it. This being said I recommend either Drain PRE (if you feel that this is an attack upon another person) or Aid PRE (if you feel that this is a boost for the player).
For the ring I suggest buying with its own abilities and then buying Computer that has personality you need. This Computer would have the Telepathy powers, most likely with O END and Only To Communicate With Wearer Of Ring.
The Telepathy power is an Instant use power that has a continuing effect. This allows it to be activated once and it will last for more than 1 segment of time as long as the person fails their Breakout Roll. For what you described Persistant and Constant are not needed as the Computer can use it many times as needed.
