The replacement of currently employed 26-pair and 27-pair cables within tactical communications Command Posts and data processing facilities has long been a goal of Army communications personnel. The use of optical atmospheric and fiber optic links offers advantages in cost, mobility, size, and security over current cable systems. The AN/TVC-4 is an advanced development model of a tactical optical communications set. It utilizes a GaAs laser diode source and an avalanche photodiode detector to provide full duplex data and voice transmission. Maximum data rate is 200 kilobits/sec with a close-confinement, single heterostructure laser diode and 5 megabits/sec with a Large Optical Cavity (LOC) laser diode. The system is designed to maintain a 10-6 probability of error (Pe) at a 3-km range under conditions of 10 dB/km atmospheric attenuation. The complete transceiver, less battery pack, is housed in a rugged 7 X 7 X 7.5 in. package which has undergone temperature, shock, vibration and humidity qualification testing. System design, component selection and performance analysis are described in detail and the results of field tests are presented.