Abstract: A subscriber loop test device is connected across a subscriber loop adjacent a subscriber equipment and remote an associated switching office. The subscriber loop test device includes a relaxation oscillator and a connection circuit responsive to a predetermined high voltage applied at the switching office for connecting the relaxation oscillator to the subscriber loop. The relaxation oscillator responds by drawing an energizing current which it modulates at the operating frequency of the oscillator. Detection of this frequency in the switching office verifies the DC and the AC continuity of the subscriber loop. Additional contacts in the connection circuit are used to disconnect the subscriber apparatus for the duration of the operation of the test device so that faulty subscriber apparatus will not interfere with verification of subscriber loop serviceability.