In Western Europe, one of the most famous and complete
Time-Code signal, widely used for Earth sciences and more, is the German
DCF77.,
transmitted from Mainflingen, near Frankfurt. It's composed of a series
of narrow (0.1) and large (0.2 s) pulses each second. The 59th is absent,
so there's a hole in the series, each minute. In each 60" time-window,
one can find a complete time information: year, month, day, day of the
week, hour, minute and second. Most of the seismic recordings, in Italy,
were carried out with this time signal reference; also our other modern
digital instruments (Lennartz M-88) use it, because of its good diffusion
on the whole Peninsula.
Below: some results of the time-signal processing made
by our MENU_HP system are shown. The 1st frame shows an automatic
processing result of the time-signal shown in the 2nd frame (in this case
it was one of the two channels digitized). The correct starting time of
the record (11:20:03.350) was produced after the stacking procedure results
(see the corrected 'X' position on the graphs), obtained from a correct
cross-correlation between the true recorded signal pulses (transformed
into coded 1, 0, -1 bits) and a synthetic one, made with all the narrow
pulses and few large (the reference pulses). The 2nd and 3st
frame show 70 s of the two digitized channels: the time and geophone
signals (vertical component). In the time-signal you can see the missing
pulse (the 59th second hole), so one can verify by hand
that the first 'pulse' is the 4th second and that the true beginning
of the trace is 3"+frac, where frac is the second's fraction,
calculated by the stacks, and equal to 0.350, in this case.
