This content summarizes all the SDH veneers, PDH veneers and data class veneers of OptiX OSN series products that support various types of loopbacks.The support capability of SDH veneers in OSN series products for loopbacks is shown in Table 1. "Y" indicates that the board supports the function, and "N" indicates that the board does not support the function.

Description of loopback on ATM/IMA boards of OSN series products

Single Board	External Port External Loopback	External Port Inner Loopback	Internal Port External Loopback	Internal Port Inner Loopback
N1ADL4	N	N1ADL4	N1ADL4	Y
N1ADQ1	N	N1ADQ1	N1ADQ1	N1ADQ1
N1IDL4	N	N1IDL4	N1IDL4	N1IDL4
N1IDL4A	N	N1IDL4A	N1IDL4A	N1IDL4A N1IDL4A N1IDL4A
N1IDQ1	N	N1IDQ1	N1IDQ1	N1IDQ1
N1IDQ1A	N	N1IDQ1A	N1IDQ1A	Y

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