This OID controls whether the test signal function configured by the paired test-signal-type object is actually active on this WAN 10G SDH interface, defaulting to off. Because it gates whether the test pattern is actually being transmitted, this is the switch an admin checks to confirm test traffic, rather than live client traffic, is currently running on the interface. For example, after configuring a specific test signal type on this interface, an engineer sets this object to enable it, runs the bit-error-rate test, and must remember to disable it again before returning the circuit to service.