What do the lights and buttons at the front of my NTU 7 mean?

The front of the NTU 7 has the following indicators and test facilities:

  • Four separate data rate indicators (green lights). These indicate the user rate in use and also double up as a power on indicator (as one of them will always be on).
  • A FAULT light (red). This indicates that the unit is in a fault state. This may be due to a self-test failure, the loss of line sync or an invalid communication message.
  • A LOCAL LOOP button. Pressing this applies a customer facing loop.
  • A LOOPBACK button. Pressing this applies a network facing loop.
  • A REMOTE LOOP button. Pressing this applies a loopback at the distant NTU.


    A yellow light, one for each loop, will come on to indicate the presence of the respective loop.

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