Confirmed TG 36964 as OLREC-4 and is encrypted. Alsip has a foot pursuit and Oak Lawn Central told all units to switch to OLREC-4. I don't know if this is permanent or the new procedure when an event is occurring on the main dispatch channel. On the old Net-6, they used to made the announcement "all units, (department) has the air" and you'd hear nothing until the incident was concluded. This might be the answer to that...unfortunately we can't hear.