Competitors send a printed message of five character groups at a specific speed, which is judged for its accuracy by a panel of referees. Like the receiving tests, there are separate competitions for sending five character groups of just the twenty-six letter of the Latin alphabet, just the ten Arabic numerals, or a mixed content of letters, numbers, and some punctuation symbols. Most transmission tests restrict the type of equipment that may be used to send the Morse code message. The Amateur Radio Call Sign Receiving Test use a software program called RufzXP that generates a score for each competitor. Rufz is the abbreviation of the German word "Rufzeichen-Hören" which means "Listening of Call Signs". In the RufzXP program, competitors listen to an amateur radio call sign sent in Morse code and must enter that callsign with the computer keyboard. If the competitor types in the call sign correctly, their score improves and the speed at which the program sends subsequent call signs increases. If the competitor types in the call sign incorrectly, the score is penalized and the speed decreases. Only one call sign is sent at a time and the event continues for a fixed number of call signs (usually 50). Competitors can choose the initial speed at which the program sends the Morse code, and the winner is the competitor with the highest generated score. The Pileup Trainer Test simulates a "pileup" situation in on-air amateur radio operating where numerous stations are attempting to establish two-way contact with one particular station at the same time. This competition uses a software program called MorseRunner. In the MorseRunner software, more than one amateur radio call sign is sent at a time. Each call sign is sent in Morse code generated at different audio frequencies and speeds, timed to overlap each other. Competitors must record as many of the call signs as they can during a fixed period of time. They may choose to do this either by recording the call signs by hand on paper, or by typing them in with a computer keyboard. The winner is the competitor with the most correctly recorded call signs. The rules of international and European championships are defined in the document IARU Region 1 Rules for High Speed Telegraphy Championships. HST competitions generally separate the competitors into different categories based on age and gender. The following are the entry categories specified in the IARU rules used for European and World Championships:  Note that there is an additional male category, which is justified by the high number of participants in the corresponding age group.