What kind of surface is required for some ELTs to activate?

Emergency Locator Transmitters (ELTs) are designed to activate under specific conditions, which often include immersion in salt water. Many ELTs utilize a special feature that triggers their activation upon contact with salt water, as salt water conducts electricity. This mechanism is particularly important in maritime environments, where ELTs are commonly deployed.

Choosing salt water as the required surface is based on the assumption that the technology within these devices is optimized for use in oceanic situations, enabling quicker activation in scenarios such as aircraft ditching. While fresh water can also activate some devices, the reliability and intended purpose of many ELTs are aligned with the characteristics of salt water.

In contrast, stating that any body of water or noting a ground surface does not accurately reflect the condition for activation that some ELTs require, as these variations may not provide the necessary conditions for operation.