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Performances of a date dissemination code on telephone lines using commercial modemsA coded time/date information dissemination system (CTD), based on telephone lines and commercial modems, is now in its experimental phase in Italy at IEN. This service, born from a cooperation with other metrological laboratories (TUG, Austria, SNT, Sweden, VSL, The Netherlands), represents an attempt towards an European standardization. Some results of an experimental analysis in which a few modems were tested, both in laboratory conditions and connected to the telephone network, in order to evaluate the timing capability of the system are given. When the system is used in a one-way mode, in many practical cases the modems delay turns out to be the main factor which limits the accuracy, even more than the telephone line delays. If the two-way mode is used, the modems asymmetry, i.e., the delay difference between transmission and reception, is almost always the most important source of uncertainty, provided the link is not including a space segment. Comparing the widely used V.22 modems to the old V.21 ones, the latters turn out to be better both in delay time (30-100 ms V.22, and 7-15 ms V.21) and asymmetry (10-50 micro-s V.22, and 10 ms V.22). Time transfer accuracies of 10 micron-s (same turn) to 100 micro-s (long distance calls) were obtained in two-way mode with commercial V.21 modems.
Document ID
19940006512
Acquisition Source
Legacy CDMS
Document Type
Conference Paper
Authors
Cordara, F.
(Instituto Elettrotecnico Nazionale Galileo Ferraris, Turin, Italy)
Pettiti, V.
(Instituto Elettrotecnico Nazionale Galileo Ferraris, Turin, Italy)
Quasso, R.
(Politecnico di Torino Italy)
Rubiola, E.
(Politecnico di Torino Italy)
Date Acquired
August 16, 2013
Publication Date
June 1, 1993
Publication Information
Publication: NASA. Goddard Space Flight Center, The 24th Annual Precise Time and Time Interval (PTTI) Applications and Planning Meeting
Subject Category
Communications And Radar
Accession Number
94N10984
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.
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