In Figure 4.2, concretely, the contact A1 is switched under no load, and the current is always switched by the switch A2. This means that, when switching on, the contact A1 closes first and the contact A2 follows similarly with the delay T1, and, when switching off, the contact A2 opens first and the contact A1 follows similarly with the delay T2. Even if the contact A2 is welded, the contact A1, which is not damaged, is able to switch off the current at least once, and the welded contact A2 is detectable by monitoring its opposite contact, B2. Two relays are allocated to A1 and A2 respectively. The delay T1 is recognized as the on-delay, and similarly, T2 as the off-delay.