Message precedence is an indicator attached to a message indicating its level of urgency, and used in the exchange of radiograms in radiotelegraph and radiotelephony procedures. Email header fields can also provide a precedence flag. Early telegraphic procedures In the early days of telegraphy and radiotelegraphy, individual countries, and sometimes individual states, sometimes set their own regulations. For example, in the period around 1909, California required that "messages must, if practicable, be transmitted immediately on and in order of receipt; if not practicable, then in the following order:" Messages from public agents of the State or of the United States on public business. Messages for immediate publication in newspapers, and not for any secret use. Message relating to sickness or death. Other messages in the order of filing. International regulation Later in the development of telegraphy and radiotelegraphy, message precedence was nominally set by the International Telecommunication Union (ITU). Various ITU Regulations provide for the following priorities: The U.S. Code of Federal Regulations, Title 47, has included the following priorities: ETAT PRIORITE FLASH EMERGENCY IMMEDIATE EMERGENCY PRIORITY EMERGENCY URGENT The current U.S. Title 47 specifies these precedence designators for radiograms: CCEB military precedence The Combined Communications Electronics Board (CCEB), a five-nation joint military communications-electronics organization (consisting of Australia, Canada, New Zealand, the United Kingdom, and the United States), uses the following message precedence designators, in descending order of importance: FLASH (Z) is reserved for initial enemy contact messages or operational combat messages of extreme urgency. Brevity is mandatory. FLASH messages are to be handled as fast as humanly possible, ahead of all other messages, with in-station handling time not to exceed 10 minutes. Messages of lower precedence are interrupted on all circuits involved until the handling of the FLASH message is completed. IMMEDIATE (O) is reserved for messages relating to situations gravely affecting the security of the nation. It requires immediate delivery. Examples include reports of widespread civil disturbance, reports or warning of grave natural disaster, and requests for or directions concerning search and rescue operations. IMMEDIATE messages are processed, transmitted, and delivered in the order received and ahead of all messages of lower precedence. They are to be handled as quickly as possible, with in-station handling time not to exceed 30 minutes. Messages of lower precedence should be interrupted on all circuits involved until the handling of the IMMEDIATE message is completed. The use of the letter "O" comes