The FOI-2170 and FOI-2171 both provide complete electrical isolation for composite video communications. The units are compatible with NTSC, PAL, and SECAM video broadcast standards. The units are transparent to all monochrome RS-170, color RS170A, and closed circuit RS-330 video. The FOI-2171 has an AGC (automatic gain control) to stabilize the video output for different fiber optic cable lengths. Adjusting the AGC potentiometer will also increase or decrease the overall scene brightness.