The TUNOL card allows the optical transmission of up to four 2Mbps signals over an optical port. The port connects two fibres, one for the transmitter and one for the receiver. The fibre can be single or multimode.

The TUNOL has four 2Mbps G.703 75 Ohm interfaces coupled with a single V.11 over head channel for management. The unit also has the 8Mbps optical port.