Patent ID: 7821758
Filing Date: 2010-10-26
Classification: H04M

Abstract:
1. A protection circuit for protecting equipment coupled to a wire pair from overvoltages, the protection circuit comprising: a first protection device having a first terminal and a second terminal, wherein the first terminal is coupled to a tip of the wire pair; a second protection device in a series arrangement with the first protection device coupled between the second terminal of the first protection device and ground; a third protection device, in a series arrangement with the first and second protection devices, having a third and fourth terminal wherein the third terminal is coupled to a ring of the wire pair; a fourth protection device in a series arrangement with the first protection device, the second protection device, and the third protection device, the fourth protection device coupled between the fourth terminal and ground; a voltage source coupled to nodes formed by the series arrangement of the protection devices, wherein at least one of the nodes to which the voltage source is coupled is between at least two of the protection devices; and an impedance device coupled between the voltage source and the nodes formed by the series arrangement of the protection devices.