The FOI-2971, FOI-2972, and FOI-4972 all provide complete electrical isolation for 2-wire telephone communications. The FOI-2972 is the low cost solution for customers using standard analog phones, STU-III (secure telephone unit) phones, fax machines, and modems. The FOI-4972 is an upgraded model of the FOI-2972 with all the same capabilities except that it can pass caller ID and operate with STE (secure telephone equipment) phones.

The units 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. FiberPlex recommends “R” units for high security applications because the units have added filtering and shielding for RFI suppression.

In addition, fiber optic cable offers much longer transmission distances than traditional telephone line cord wiring. Multimode optics on the units can extend the distance to 2km, while singlemode optics can further extend the distance to 20km. A typical link consists of an FOI-2971 connected to the POTS line and an FOI-2972 or FOI-4972 at the subscriber’s phone with a duplex fiber optic cable between them.