Complex sentence: The use of a franking privilege is not absolute but is generally limited to official business, constituent bulk mails, and other uses as prescribed by law, such as the "Congressional Frank" afforded to Members of Congress in the United States.
Split into simpler sentences: The use of a franking privilege is not absolute but is generally limited to official business, constituent bulk mails, and other uses as prescribed by law. A primary example of this type of limited privileged franking is the "Congressional Frank" afforded to Members of Congress in the United States.