In an FM-phone signal, what is the term for the maximum deviation from the carrier frequency divided by the maximum audio modulating frequency?

The term for the maximum deviation from the carrier frequency divided by the maximum audio modulating frequency is known as the deviation ratio. This ratio is a crucial parameter in frequency modulation (FM) as it characterizes how much the carrier frequency can vary in response to the modulating signal.

In FM, the carrier frequency shifts away from its resting frequency by a certain maximum amount, called the maximum deviation, based on the amplitude of the audio signal being fed into the modulator. The maximum audio modulating frequency refers to the highest frequency present in that audio signal. By calculating the deviation ratio, one can assess the extent of modulation and its potential effect on the transmitted signal's quality and bandwidth.

Other terms like modulation depth, deviation index, and frequency ratio refer to different concepts in modulation and signal processing. Modulation depth usually refers to the extent of modulation in an amplitude modulation scenario, while deviation index is associated with the amount of modulation in terms of phase modulation rather than frequency modulation. Frequency ratio isn't a standard term used in the context of FM modulation. Hence, the deviation ratio stands out as the correct choice in this context.