The 3RT1 contactors are suitable for use in any climate. They are safe from touch to DIN VDE 0106 Part 100. The 3RT1 contactors are available with screw connections or with cage clamp connections. The basic units of sizes S0 to S3 only contain the main conducting paths. All the basic units can be extended with auxiliary switch blocks. 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. 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.