There are 4 main categories of equipment to make connections SDH:
• Switch card: This card provides the functions of multiplexing and circulating traffic between line interfaces and other interfaces. Its capacity is equivalent to 12x12 STM - 1, without limitation ( "non-blocking matrix"). This card can be split to ensure protection.
• The line cards (STM-1, 4.16 ..): These cards provide optical transmission signals STM. They are not split. The failure of one of them does not the protected traffic as it is transmitted simultaneously interfaces on the "East" and "West".
• The multiplex controller module: this card provides the functions of central control and safeguard the configuration. It is not split because its failure does
not disrupt traffic.
• The communication card: This card provides the functions management to network management. It is routed through the signal STM online. This map is not split because its failure does not disrupt the traffic.