Abstract: A contact arrangement includes a first electrical contact, a second electrical contact and a measuring device for determining a contacting state between the first and second contacts. In a first contacting state the first and second contacts are electrically isolated from one another, and in a second contacting state the first and second contacts are electrically connected to one another. The measuring device includes an acoustic signal transmitter for transmitting an acoustic signal into the first contact, and a signal receiver connected to the second contact in a sound-conducting manner.

Abstract: A monitoring device for monitoring an impedance of a protective conductor. The monitoring device has a first voltage divider for connection to a voltage source including a series connection to a first resistor and a second resistor. The second resistor has a resistance value which corresponds to a threshold value for the impedance of the protective conductor. A second voltage divider includes a series connection to a third resistor and a bridge diode and a connection to the first resistor at a first end of the third resistor and connectable to a second end of the third resistor and to the protective conductor. A measuring device is provided for the detection of a bridge voltage between a first node and a second node if the impedance of the protective conductor is greater than the value of the second resistor.

Abstract: A contact arrangement includes a first electrical contact, a second electrical contact and a measuring device for determining a contacting state between the first and second contacts. In a first contacting state the first and second contacts are electrically isolated from one another, and in a second contacting state the first and second contacts are electrically connected to one another. The measuring device includes an acoustic signal transmitter for transmitting an acoustic signal into the first contact, and a signal receiver connected to the second contact in a sound-conducting manner.

Abstract: A monitoring device for monitoring an impedance of a protective conductor. The monitoring device has a first voltage divider for connection to a voltage source including a series connection to a first resistor and a second resistor. The second resistor has a resistance value which corresponds to a threshold value for the impedance of the protective conductor. A second voltage divider includes a series connection to a third resistor and a bridge diode and a connection to the first resistor at a first end of the third resistor and connectable to a second end of the third resistor and to the protective conductor. A measuring device is provided for the detection of a bridge voltage between a first node and a second node if the impedance of the protective conductor is greater than the value of the second resistor.