This CoriantTypesTestSignalType value (default NONE) selects which standard test pattern an STM-64 (10 Gb/s SDH) client port generates when test-signal mode is active, used to verify the facility independent of live customer traffic. An administrator selects a specific test pattern to match what the test equipment or far-end node expects to receive during commissioning or fault isolation. For example, a technician bringing up STM-64 for the first time might select a defined test pattern here so a test set on the far end can verify bit-error performance before real traffic is switched on.