Which of the following is not a main component of the FPS hand held radio?

The tone button is not considered a main component of the FPS handheld radio. Handheld radios commonly include essential components vital for their basic operation and functionality, such as an on/off/volume button, which controls power and sound levels; a squelch button, which eliminates background noise; and an antenna, which is crucial for receiving and transmitting signals effectively. While tone features can enhance communication or alert functions, they are typically not classified as fundamental components necessary for the device's core operation. Therefore, identifying the tone button as the correct answer highlights an understanding of the basic structural and functional elements of handheld radios.