The FOI-2981, FOI-4982, and FOI-2983 all provide complete electrical isolation for audio communications. The unit can be used in areas of high electrical noise or in and out of RF shielded enclosures. The fiber optic cable is not susceptible to interference caused by impulse noise, crosstalk, or EMI. Privacy of communications is also enhanced because the fiber optic cable does not radiate any emissions. In addition, fiber optic cable offers much longer transmission distances than copper wiring. Multimode optics on the units can extend the distance to 2km. A typical link consists of either an FOI-2981 or an FOI-2983 at one end of the network transmitting optical signals to an FOI4982 at the other end of the network with a single fiber optic cable between them.