The 3RT1 contactors can be retrofitted with RC elements, varistors, diodes or diode assemblies (combination of an interference suppression diode and a Zener diode for short tripping times) for suppressing opening surges in the coil. The surge suppressors are plugged onto the front of size S00 contactors. Space is provided for them next to a snapon auxiliary switch block. With all size S0 to S3 contactors, varistors and RC elements can be plugged on directly at the coil terminals, either on the top or underneath. Diode assemblies are available in two different designs with different polarities. Depending on the application, they can be attached either only on the bottom (assembly with circuit breaker) or only on the top (assembly with overload relay).