The FOM-3841 and FOM-3842 provide complete electrical isolation for four independent channels of 2-wire telephone communications. The FOM-3842 supports standard analog phones, STU-III (secure telephone unit) phones, STE (secure telephone equipment) phones, fax machines, and modems and supports Caller ID.

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. 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 FOM-3841 connected to the POTS line and an FOM-3842 at the subscriber’s phone with a duplex fiber optic cable between them.