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There was no need, really. The university's networking/telecommunications group ran their own pair of stratum-1 NTP servers, plus four stratum-2 NTP servers, so my stratum-1 wasn't really needed. I ran my stratum-1 NTP server simply because the hardware was available and I had an interest in it. You see, the GPS clock (and its predecessors, a WWVB clock and a pair of GOES clocks) were relics of a time long past...

[insert wavy flashback transition here]

The lab I mentioned was a seismological observatory. In the days before cheap, high-resolution A/D converters and computers with massive amounts of storage existed, almost everything was analog. Gloriously, unashamedly analog.

Seismograph stations sent data from their seismometers back to the lab over a "dry loop" — a leased line with no dial tone or voltage on it — from AT&T. To do this, the seismometer's output signal was greatly amplified, then frequency modulated onto a relatively low frequency carrier (1–2 kHz). The signal then traveled through AT&T's network all the way to the lab, where the signal was demodulated.

Okay, great, we're getting the signals back at the lab, but how do we store these waveforms? The answer is a giant drum, a motor, some paper, and a pen or stylus — a drum recorder.

http://www.aeic.alaska.edu/input/west/proj/ASRA/2007/picture...

"Helicorder" was Teledyne Geotech's brand name for their line of drum recorders, but it was so popular that "helicorder" has become a generic name for "drum recorder" in the seismological community, much like "Xerox" became synonymous with "photocopier." (If you ever look at earthquake records on-line, check for "heli" in the URL.)

A piece of paper is wrapped around the drum. A pen/stylus rests on the paper and deflects side-to-side depending on the polarity and magnitude of the input signal. A big positive voltage makes the pen move really far to one side, and a small negative voltage makes the pen move not so far to the other side. The pen is also attached to a threaded shaft that rotates, slowly moving the pen from one side of the paper to the other. The drum itself also rotates, and the rotation speed of the drum and the shaft was usually selectable — most people had recorders with small drums set to record ~24 hours of data per piece of paper, with wider drums set to record for a proportionately longer amount of time. (The higher the drum speed, the better the record quality, but then you had to change the paper more often.)

So we can record the signal onto paper, but we're missing a very important thing — time. We need to know exactly when stations saw ground motion in order to locate earthquakes and other seismic events. Enter the GPS clock (and the WWVB clock and GOES clocks before it). The GPS clock received a very accurate time signal and was configured to output a very simple timecode known as "slow code." Slow code works as such:

• At exactly the start of the 0'th second of every minute, generate a voltage pulse for some amount of time, usually 2 seconds.

• At exactly the start of the 0'th second of the 0'th minute of every hour, generate a voltage pulse for some longer amount of time, usually 4 seconds.

• At exactly the start of the 0'th second of the 0'th minute of the 0'th hour of every day, generate a voltage pulse for some even longer amount of time, usually 6 seconds.

This slow code would be added to the signal being recorded by the drum recorder, adding precisely timed "bumps" to the record. When the paper was changed on the drum every 24 hours, someone would write or stamp several pieces of information on the paper: the seismograph station's name, the date, and the time of the first time mark:

http://www.hilo.hawaii.edu/~nat_haz/earthquakes/media/SeisDE...

Note the column of time marks between the stamped dates. The narrow marks are minute marks, the slightly wider marks are hour marks, and the widest mark (five lines above the little earthquake) is the day mark.

[insert wavy flash-forward transition here]

Eventually, everything at the seismological observatory went digital, and the seismograph stations were upgraded with digitizers that had their own GPS clocks for timestamping data. The WWVB clock and GPS clock sat unused until I cleaned them up and reconfigured them to serve up time for ntpd to consume.