The TMX-ISDN provides complete electrical isolation for 2-wire U-Interface and 4-wire S/T-Interface ISDN communications. The unit has four channels that are independent of each other with two switches each that allow users to select between different ISDN modes and interfaces. The “TO LT” (line terminal) mode is associated with only the U-Interface, while the “TO TE” (terminal equipment) mode is associated with only the S/T-Interface. The U-Interface and S/TInterface will both operate in the “TO NT” (network terminal) mode.

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. The potential problem of creating ground loops or ground offsets is also eliminated because signal ground is not carried over the fiber. The unit enhances privacy of communications because fiber can not be tapped without being detected and does not radiate any emissions.

A typical link consists of two TMX-ISDN, one at each end of the network with a duplex fiber optic cable between them. Users can also create a link between the U-Interface and the S/T-Interface without requiring a separate interface converter, such as an NT-1.