4-WIRE/2-WAY RADIO INTERFACE (DUAL) The FOR-22 connects two external 4-wire circuits to the matrix. Camera intercoms, two-way radios, microwave and satellite links, IFBs, and program audio inputs and outputs are candidates for the FOR-22. The module provides proper impedance matching, transformer isolation and level adjustments between systems. It also supports external relay activation and call-sense circuitry. The relays can be controlled separately to add to the frame relay complement.