Remote extensions

I have installed a test system in my office and I am trying to get remote extensions to work. I have DSL in the office. I can get the phones to register (from my house) but I cannot get any audio. I can hear ring back tone when I dial an extension but I am not certain if it is ring back from the softphone on my laptop or ring back from the machine in the office. At any rate, once the connection is made audio ceases.