Abstract: An arrangement for performing subscriber loop testing through a concentrator/expandor employing semiconductor crosspoints. The crosspoints of the concentrator/expandor are relatively nonlinear when conducting currents less than a predetermined current and are relatively linear when conducting currents in excess of the predetermined current. When tests are to be applied to a given subscriber loop which comprises a tip conductor and a ring conductor, two paths are completed through the concentrator/expandor to the tip conductor and two paths are completed through the concentrator/expandor to the ring conductor. A linearizing source then transmits a current in excess of the predetermined current around the circuits formed by the two concentrator/expandor paths to each subscriber loop conductor. Test signals are then applied to the subscriber loop by connecting such signals between the two paths to the subscriber ring conductor and the two paths to the subscriber tip conductor.