Kramer Electronics OC-4 OC-4 is a high performance optical isolator for video or sync signals. It provides complete isolation between devices thus eliminating video hum, ground loops, and DC offsets which can degrade picture quality. Bandwidth - 20MHz (-3dB). Channels - 4. Opto-Isolator Circuitry - Extremely linear response and wide frequency range compared to traditional transformer based units. Level (Gain) and EQ (Peaking) Controls. Floating Ground Selection - Input, output, both, or none. Standard 19inch Rack Mount Size - 1U.