A safety switching device for fail-safe disconnecting an external load that has a first pole and a second pole, comprising: a first terminal for receiving a first potential, a second terminal for receiving a second potential, a first switching element between the first terminal and the first pole of the external load , a second switching element between the second terminal and the second pole of the external load , a signal processing unit configured to receive a switch-off signal via an input and to actuate, based on the switch-off signal, the first and second switching element , an internal load , and a third switching element configured to connect the internal load in parallel with the external load , wherein a first read-back point is arranged between the first switching element and the first pole , a second read-back point is arranged between the second switching element and the second pole , and a third read-back point is arranged between the third switching element and the internal load , wherein the signal processing unit includes a testing device and a memory in which a first set of error patterns is stored, wherein the testing device is connected to the first, second and third read-back point and is configured to perform a first switching test having at least three test intervals (78, 80, 82; 84) separated in time, wherein the testing device is configured to receive a read-back signal in each test interval (78, 80, 82; 84) at the first, second and third read-back point to generate a first test pattern , wherein the testing device is further configured to match the first test pattern with the first set of error patterns to determine an error . a first terminal for receiving a first potential, a second terminal for receiving a second potential, a first switching element between the first terminal and the first pole of the external load , a second switching element between the second terminal and the second pole of the external load , a signal processing unit configured to receive a switch-off signal via an input and to actuate, based on the switch-off signal, the first and second switching element , an internal load , and a third switching element configured to connect the internal load in parallel with the external load , wherein a first read-back point is arranged between the first switching element and the first pole , a second read-back point is arranged between the second switching element and the second pole , and a third read-back point is arranged between the third switching element and the internal load , wherein the signal processing unit includes a testing device and a memory in which a first set of error patterns is stored, wherein the testing device is connected to the first, second and third read-back point and is configured to perform a first switching test having at least three test intervals (78, 80, 82; 84) separated in time, wherein the testing device is configured to receive a read-back signal in each test interval (78, 80, 82; 84) at the first, second and third read-back point to generate a first test pattern , wherein the testing device is further configured to match the first test pattern with the first set of error patterns to determine an error . <EOS>