Optical Isolator is used to connect a PC/Terminal and another device directly to protect your PC/ Terminal/Device from the constant threat of ground loop currents and voltage surges. These Isolators are incredible ! By converting signals into light beams internally, their advanced design lets your data ignal go through, but a voltage spike is blocked. Your PC/Terminal/Device are effectively isolated from any surge, upto 1500 volts. These surges can be caused by various sources ? lightening, static buildup or interruptions in AC power supply. Your systems must have these Isolators if your cable runs close to AC power lines.