Your answer is if you want to get the value of keypair value system you need to use it like this way
var objects = this.responseText;
objects.system[0].S Answer ----> 30 ;
objects.system[1].S Answer ----> 24 ;
objects.system[0].T Answer ----> 20121107130000;
objects.system[0].L Answer ----> 213;
objects.system[0].ObjectName Answer ----> 14. Rummet
objects.system.length Answer ----> 2