Patent ID: 7948121
Filing Date: 2011-05-24
Classification: H01H,H03K

Abstract:
1. A safety switching apparatus for failsafe shut-down of an automatically operated installation in response to a first and a second signal from a two-channel signaling device, with the first and the second signal each having a defined polarity, the safety switching apparatus comprising: a first terminal for supplying the first signal and a second terminal for supplying the second signal, a first and a second switching element, which together are designed to produce a redundant output switching signal for shutting-down the installation, a first control circuit connected to said first terminal and to said first switching element for supplying said first signal to said first switching element, and a second control circuit connected to said second terminal and to said second switching element for supplying said second signal to said second switching element, wherein said second control circuit includes a first current path and a second current path and at least one further switching element, wherein the at least one further switching element is designed to rout the second signal to said second switching element either via the first current path or via the second current path, depending upon the polarity of said second signal, wherein said second control circuit comprises a plurality of diodes forming a bridge rectifier, wherein the bridge rectifier has a first and a second bridge terminal, with the second switching element being arranged between the first and second bridge terminal, wherein the bridge rectifier has a third and a fourth bridge terminal, with the third bridge terminal being coupled to the second terminal, and with the fourth terminal being connected to a defined reference potential, wherein the at least one further switching element comprises at least one switching transistor designed to selectively connect the fourth bridge terminal to one of two different reference potentials, and further wherein the second control circuit further comprising a control unit designed to toggle the at least one switching transistor in order to alternately connect the fourth bridge terminal to one of the two different reference potentials until a flow of current is detected in the second switching element.