HP HSR6800 Configuration Manual page 51

Shutting down/bringing up a T1 line also shuts down/brings up the serial interface formed by it and the
serial interface created on it by means of timeslot bundling.
To shut down/bring up only a serial interface formed by T3 or T1 lines, or by timeslot bundling on a T1
line, perform the shutdown/undo shutdown command in the view of the corresponding serial interface.
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