Which component allows a transceiver in sleep state to be activated via radio?

The component that allows a transceiver in a sleep state to be activated via radio is the wakeup receivers. This specific functionality is important in various wireless communication systems, particularly in energy management and IoT (Internet of Things) applications, where devices often need to conserve power while still being responsive to external signals.

Wakeup receivers operate by continuously monitoring for specific wakeup signals, even when the transceiver is in a low-power state. When the receiver detects a designated signal, it triggers the transceiver to exit sleep mode and become fully operational. This design is crucial for maintaining energy efficiency while ensuring that devices can still respond promptly to communications or commands.

In contrast, idle protocols are generally used for maintaining connections and managing data flow when a device is in a low-power state, but they do not specifically facilitate waking a device up via radio signals. Power buttons are physical mechanisms for activating devices but do not relate to remote activation via radio. Radio transmitters typically send signals rather than receive them, thus are not responsible for waking up a sleep state transceiver.