The switching of contactor coils can generate voltage transients that may cause arching on switch contacts and damage electronics on the control line. Either an RC or varistor suppressor is recommended in these types of applications. All XT DC contactor coils have built-in suppression. Varistor suppressors clamp the voltage transient above the maximum coil voltage and are recommended when the level of the transient is known to not exceed the coil voltage. RC suppressors slow and reduce the level of the voltage transient but do not clamp them at a specific level. The slowing of the transient can reduce electrical interference. These are recommended in applications where operating rates are high.