This from Chris Ranck:
this from carma chicago; NORTHWEST CENTRAL is switching to a new radio system , it will be a new STARCOM 21 system . It will be a new tdma system which is a non-monitorable radio system . They are supposed to switch on MARCH 26 2013 . They will be switching the old digital system first, towns like ELK GROVE , ARLINGTON HEIGHTS, BUFFALO GROVE etc…… 2) SCHAUMBURG system and finally STREAMWOOD and HOFFMAN ESTATES systems. Since it’s tdma, scanners won’t be able to recieve it .