Which Emergency Locator Transmitter (ELT) has an ON/OFF switch?

The correct choice is the portable Emergency Locator Transmitter (ELT). Portable ELTs are designed with user-friendliness in mind, allowing individuals to easily operate them. The inclusion of an ON/OFF switch is a key feature that enables users to activate or deactivate the device as needed, promoting quick accessibility during emergencies.

In contrast, fixed mount ELTs, for example, are typically integrated into the aircraft's structure and are generally activated automatically upon a crash impact. They do not possess a manual ON/OFF switch for user control in the same way portable options do. Similarly, while there are larger and smaller ELTs, they mainly refer to the physical size of the devices and may not encompass the functionality of manual operation that characterizes portable ELTs.

Thus, the design and purpose of portable ELTs, which include an ON/OFF switch for manual operation, make them the appropriate choice in this context.