What type of current involves the machine interrupting the flow for brief periods?

Pulsed current is characterized by its intermittent flow, where the current is switched on and off in brief cycles. This results in short bursts of electrical activity, which can be beneficial for various therapeutic applications, such as in electrical stimulation treatments. The interruptions create a unique pattern of current that can help in muscle contraction or pain relief, allowing for more controlled delivery of stimulation.

In contrast, direct current provides a continuous, unidirectional flow of electricity, while alternating current involves a bidirectional flow that periodically reverses direction. Continuous current denotes a steady and uninterrupted flow, unlike pulsed current, which has distinct intervals of no flow. Therefore, pulsed current's very nature of interruptions makes it the correct choice for the question regarding the type of current that involves the machine interrupting the flow for brief periods.