Crane digital engine controls (DEC9000, DEC9500 and mini-DEC series) and ignition systems (HI-6, HI-6S, and HI-6DI2) have inputs used to select rev limit and/or retard stages. In some applications, these inputs are directly connected to external circuitry that may include solenoids (or solenoid operated valves) controlled by a switch or relay. Common examples include line lock and transmission brake solenoid valves connected to a stage limit input and nitrous oxide injection solenoid valves connected to a retard input.

When the switch or relay opens and current flow to the solenoid is interrupted, very large electrical transients (500 volts or more) may occur. These transients can lead to glitches in the electronics. Arcing also occurs in the switch contacts. Arcing greatly decreases switch life and may result in erratic operation. These conditions may cause inconsistent launch and 60 foot times.

Other large inductive loads, such as a throttle stop solenoid, may cause severe electrical glitches, even if these devices are not directly connected to any engine control or ignition system.

Inexpensive surge absorbers, also referred to as MOVs (metal oxide varistors), installed directly across all solenoids eliminate problems with switching transients.

Some solenoids have current draws in excess of 10 amps. Switching of these devices may cause excessive jumps in the 12 volt supply. A filter capacitor is recommended.