Switchboard 100 Central Office (CO) Cables are designed for indoor use in CO exchanges, or in premises telephone rooms. These cables are used for interconnection of distribution frames and digital switching and transmission equipment systems. Switchboard 100 provides 100 Ohm characteristic impedance. The product line consists of 24 or 26 AWG tinned insulated copper wires that are twisted into pairs. The pairs are stranded together utilizing a standard color code scheme.