Image Number 2 for United States Patent #4319092.
Current detection circuit arrangement for an automatic telephone exchange for detecting currents in a system of two conductors having earth as the common return conductor. This circuit arrangement comprises a pair of measuring resistors R.sub.1, R'.sub.1 and a pair of voltage dividers R.sub.2, R.sub.5 and R.sub.3, R.sub.4 which are connected cross-wise and form a bridge. The loop current I.sub.d can be detected with this circuit arrangement. It is also desirable for the circuit arrangement to enable the detection of the longitudinal currents in the conductors. The present circuit arrangement comprises a pair of connecting points for a detector for the longitudinal currents, one point of which is connected to the tapping point of one and to the tapping point of the other voltage divider, respectively, by way of separate resistors, the other point being a point of reference potential.