HARFORD COUNTY, MD. — Marlton, N.J.-based L-3 Communications’ Command & Control Systems and Software, a defense firm, has signed a full-building lease with St. John Properties for a 75,000-square-foot office building. The space is located in Aberdeen Proving Ground’s Government and Technology Enterprise project at 6280 Guardian Gateway in Harford County. The building is now under construction and has been designed to achieve Silver LEED certification. Green features include a highly efficient HVAC system, low-flow fixtures and drought-tolerant landscaping. Delivery is expected in fall 2010.