Precise Time and Time Interval (PTTI) is a Department of Defense Military Standard which details a mechanism and waveform for distributing highly accurate timing information.
It is similar to Pulse per second (PPS) because it indicates the start of each second using a pulse. PTTI also provides the full Time Of Day (TOD) in hours, minutes, and seconds.
References
Precise Time and Time Interval Wikipedia(Text) CC BY-SA