Digital Audio Playback; Mackenzie Laboratories is a Leading Developer of Digital Audio Messaging Systems for a Wide Variety of Applications Including, Airports, Conference Centers, Mass Notification, Safety and Evacuation, Hospital Code Blue Systems, Museums, Theme Parks, Message-On-Hold, Storecasting, and Overhead Paging. Comprehensive In-Vehicle and Platform Transit Audio Systems. Offering Design and Integration Services, Using over 60 Years of Industry Leading Experience to Develop Custom ...