Empty String Equals To Blank: How To Change This Behaviour?

This seems to be a rather old problem (http://www.themssforum.com/SQLServer/Does-empty/) but I couldn't find an answer yet.

The problem is: I have two tables t1 and t2 where t1 is a staging area of t2.
t1: (id int not null, phone varchar(30))
t2: (id int not null, phone varchar(30))

Data in t1: (1, '') <- empty string
Data in t2: (1, ' ') <- a blank

Comparing t1.phone with t2.phone results in equality which in my opinion isn't correct.

The question ist: How can I change the behaviour of SQL-Server to result in inequality so that the change in my staging table is detected correctly?

Thanks in advance
Fridtjof