How did police officers on patrol in Chicago initially engage in two-way communication with the dispatchers at police headquarters? The officers on the beat would meet up on a street corner and pass messages from one officer to another until every officer on patrol had received the dispatcher’s message The dispatcher would light a red flare and stand atop the headquarters building summoning officers in from patrol They would drive by the station every hour or so just to check in The officer on patrol would stop by a signal box every hour and send a telegraphic message to the dispatcher asking if there were any messages or calls for service in his area of patrol.