27 00 00 Communications
27 01 00 Operation and Maintenance of Communications Systems
27 01 10 Operation and Maintenance of Structured Cabling and Enclosures 27 01 20 Operation and Maintenance of Data Communications 27 01 30 Operation and Maintenance of Voice Communications 27 01 40 Operation and Maintenance of Audio-Video Communications 27 01 50 Operation and Maintenance of Distributed Communications and Monitoring