The 104A zone controller meets the LonMark open protocol profile for rooftop controllers, says TAC Controls (Grandville, MI). It is designed to be used on an Echelon TP-FT10 LonWorks open protocol network or operate as a stand alone controller. The 104A complements the company's present line of zone controllers for vav boxes, fancoil units, and hvac single-zone equipment. It can be connected by way of Echelon network directly to the company's Vista Central System front end.