Virtually all of Spellman's supplies (with the exception of a few modular proportional supplies) are "current protected." Current protection is accomplished through the use of a regulating current loop, otherwise known as current mode.

The current mode is programmed to a regulating level via the front panel pot or the remote current programming signal. A current feedback signal is generated inside the supply that drives the current meter (if there is one) and the remote current monitor signal. By comparing the current feedback signal to the current program signal, the supply can limit or regulated the output current to the desired level. Even if a continuous short circuit is placed on the output of the supply, the current mode will limit the output current to the desired preset level.