The characteristics of typical timing signal generating systems are discussed. These general serial time codes, usually a succession of 0 to 5 volt DC pulsed from 10 to 10,000 HZ. Such generators produce signals for Time Pulse codes, Coded Time Pulse Codes, IRIG Time and Control Code, NASA Time and Control Code and SJ1PTE Time and Control Code. These signals are often generated together with the decoder and driving current, or the signal will be inputed from outside sources, decoded and converted into drives to pulse the light emitting diodes displays in "on camera" film data annotation systems. Typical time data annotation systems include simple camera timing markers for exposing a narrow time or data track along the edge of the continuously moving film. Systems which record 9 or more digits of time and other data on each frame of film are: BCD, i.e., 4 x 9 numeric data annotation systems; 7 segment LED characters for recording numeric time or hexidecimal information; lastly, data annotation systems using 5 x 7 LED matrices to record full alphanumeric (ASCII) characters, including numeric time. The advantages and limitations of these systems are considered.