What is true about the SONET transmission standard?

The SONET (Synchronous Optical Networking) transmission standard is indeed the North American standard primarily designed for telephony applications. This standard provides a framework for transmitting digital information over optical fiber using synchronization methods that ensure reliable and efficient data transfer. SONET systems are essential for telecommunications networks because they allow different types of data, such as voice and data traffic, to be multiplexed and transmitted over a network efficiently.

The standard includes various rates, which help in accommodating the demands of telephony services and other types of communication. It is significant in creating a robust infrastructure for connectivity and high-capacity transmission, making it fundamental to North American telecommunication systems.

While SONET does utilize fiber optic technology predominantly, it is not limited to supporting only fiber optic cables, as there are implementations using other media. Additionally, SONET is specific to the North American context, whereas other similar standards exist worldwide, making it not a global standard on its own. Therefore, identifying SONET as primarily used for telephony applications aligns with its design and functional purpose in the telecommunications realm.