An atmospheric lasercom link over a 4 km path has been implemented between The MITRE Corporation and Lahey Clinic, Bedford, MA. This testbed employs emerging 1550 nm laser and receiver technology for greatly enhanced covertness and eye safety compared to current 820 nm technology. Supporting testbed equipment provides automated monitoring of link performance, correlated with automated data acquisition of the local visibility and precipitation. This report describes the laser link and supporting testbed equipment under IBM PS/2 computer control in which continuous monitoring of the atmospheric conditions, link bit error rate, pointing jitter, and beam wander are accomplished. The bit error rate drives an automated adaptive data rate modem at one of three data rates, depending on weather conditions. Criteria for operation at 1550 nm, such as trade-offs with regard to atmospheric absorption, covertness and eye safety are presented. Characteristics of our custom designed laser transmitter (laser diode, beam parameters, modulation, etc.), and receiver (optics, detector electronics, bit synchronizer) are described. System alignment procedures and transmission performance as a function of temperature, visibility, and precipitation are presented.