| 摘要 |
A telecommunication network and switching system where digital circuits are supplied to customer terminals for dial-up services and where automatic testing of the access connections to the customer premises is performed while calls are not in progress. A loop test unit is provided at the customer's premises near to the customer digital line terminals able to detect a test sequence sent from an exchange when a call is not in progress, the test sequence being recognized by the loop test unit and a test sequence being returned to the exchange to enable the error performance of the link in both directions to be tested.
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