Meaning
Precision timing signals consisting of a single electrical pulse occurring exactly once every second provide a reference for aligning the phase of multiple clocks. Leading edges of the waveform mark the transition from one second to the next with high accuracy. Comparing a pulse per second from two different sources allows for the direct measurement of phase offset without the complexity of network protocols.
Signal Frequency
Most global navigation satellite system receivers output this signal to allow external hardware to synchronize to atomic time. By using the pulse per second, a local oscillator can be disciplined to match the frequency and phase of a master reference. This method provides a physical verification of timing accuracy that is independent of software-based measurements.
Physical Verification
Oscilloscopes and time interval counters use the physical voltage spike to measure the alignment between two devices. Distribution of pulse per second signals over coaxial cable requires careful management of cable length to prevent phase shift. A nanosecond of delay is added for every few centimeters of wire, making calibration a necessary step in high-precision laboratory and production setups.
Timing Precision
Synchronization at the nanosecond level is only possible when the rise time of the pulse is sharp and the electrical noise on the line is minimal. Maintenance of signal integrity is the primary challenge when distributing this reference across a large data center.
