Cisco pays special attention to its network accessories, which are the foundation stone of the whole network system. The company offers a variety of connectivity, expansion and upgrade options to accommodate the customer specific needs. Cisco's components are easily and inexpensively upgradeable as customer requirements change.The 4-port fiber Token Ring module provides four additional Token Ring connections for the base Catalyst 3900 Token Ring switch. The ports of this expansion module support four pairs of multimode fiber connections via ST-type optical transmitter and receiver ports.