Patent ID: 7327157

Claim:
A switch device, comprising: a switch to be tested with a first terminal and a second terminal as well as a control terminal for controlling a resistance between the first terminal and the second terminal; a resistor; a second switch connected between the control terminal and the first terminal of the switch to be tested, wherein the control terminal and the first terminal of the switch to be tested are coupled conductively when the second switch is closed; a drive circuit with a control output, wherein a control voltage for controlling the switch to be tested can be provided at the control output, and wherein the driver is formed to optionally switch the switch to be tested on or off, wherein the control voltage is present at the control output of the drive circuit, and wherein a third switch is connected between the control output of the drive circuit and the control terminal of the switch to be tested, wherein the control output of the drive circuit and the control terminal of the switch to be tested are conductively connected when the third switch is closed; a switch controller for controlling the second switch and the third switch, wherein the switch controller is formed to open the second switch and close the third switch in a first mode of operation, and close the second switch and open the third switch in a second mode of operation; and a sensor for sensing a voltage present due to a measuring current across the resistor into the first terminal of the switch to be tested between the control terminal and the second terminal of the switch to be tested, wherein the voltage refers to an operability of the switch to be tested.