The physical boards of the SEP and the SEP1 are the same, but the logical boards are different.
1. The logical board of the SSN1SEP1 on the OptiX OSN 3500 can be set to SEP or SEP1. When set to the SEP, the board works with the interface board. When set to the SEP1, the board provides interfaces on its front panel and therefore does not need an interface board. (The SEP works with the EU08, OU08, or EU04 interface board; the SEP1 board provides 2xSTM-1 electrical interfaces.)
2. When working with the interface board, the logical board of the SSN1SEP1 is set to the SEP, which processes 8xSTM-1 electrical signals. The EU08 and the OU08 boards are 8xSTM-1 interface boards that work with the SEP board; the EU04 board is a 4x-STM-1 interface board that works with the SEP board. The TSB4 and the TSB8 are electrical-interface protection switching boards. The SEP works with the interface board and the bridge board to provide the TPS function.
3. When the GXCSA board is used, the logical board can be set to the SEP1, which provides interfaces on its front panel. Alternatively, the logical board can be set to the SEP, which works with the EU04 board. Note that the board cannot work with the OU08 or EU08 interface board when the GXCSA board is used. 4. The SSN1SEP1 board can support up to two ECCs. The SEP board cannot support ECC.