Which of the following is NOT one of the three types of disconnects?

The answer identifies that a relay switch is not categorized as one of the three main types of disconnects. Disconnects are devices that isolate electrical circuits or equipment from the power source for maintenance and safety purposes. The primary types of disconnects include fuse blocks, breakers, and knife switches, each designed to serve this purpose effectively.

Fuse blocks are used with fuses to protect circuits from overloads, while breakers are designed to interrupt the flow of current automatically during overload conditions. Knife switches provide a manual method of disconnecting power by physically separating the circuit.

In contrast, a relay switch is primarily used in control circuits to operate other devices and is not specifically designed for disconnecting power. Thus, identifying the relay switch as the option that does not align with the primary functions of disconnects highlights its different role in electrical systems.