While taking a shower and someone turns on water in another part of the house the cold water stops to the shower and I get scalded. What can be done?

How old is your home and are your water pipes galvanized?
This is a part of problem usually cause by rust blockage the flow. The solution would be to repipe your house with plastic. I'm sorry to be the bearer of bad news but that's the only solution I know. Good luck, Tom

Hmmm..

I'd like to know if this shower valve has a single handle or two or three handles, perhaps?

If this is a two or three handle shower valve then the issue is with the valve itself... not anti.-scald. The only fix for this is to be sure no one uses cold water in the house while you are showering OR you need to change the two/three handle shower valve over to a single handle shower valve as these are anti.-scald protected and will resolve the issue.

If this is a single handle shower valve and the issue is a new issue then it could be that the balancing spool is shot... maybe?

Post back with more info...

Mark