2 Chapter 1
Introduction to the MTU-TXC
2
Introduction to the MTU-TXC
The MTU-TXC is a GPS-satellite-synchronized clock
used to control geophysical current sources and
provide timing signals to receivers. The MTU-TXC takes
as input a schedule of frequencies in the time domain
or frequency domain, and controls the connected
current source or receiver according to that schedule.
Various schedules can be saved in files on the unit’s
data directory. The operator chooses which schedule to
use by connecting a PC and changing a single
parameter using a small utility program.
Available frequencies
The MTU-TXC derives its frequencies from a 921.6kHz
signal, and therefore it may not be able to produce
exactly the requested frequency. Use at least 6
(preferably 8) significant digits when specifying a
frequency. The MTU-TXC will produce the closest
approximation possible.
About phase
For synchronization with other Phoenix GPS-equipped
instruments, the output phase is such that if the
waveform were extended backward in time, the centre
of the positive on time (or the negative on time in
unipolar negative) would align with 2000/01/01
00:00:00 UTC. (UTC leap seconds are ignored for this
purpose.)
Note Leap seconds may occur at the beginning of January
or July every few years, as determined by the
International Earth Rotation and Reference Systems
Service (IERS). If a leap second happens to occur
while the MTU-TXC is generating a waveform, there
may be a discrepancy of 1s in its phase. To prevent
problems, consult the IERS Web site
(http://www.iers.org/) for notifications and avoid
transmitting during the occurrence of a leap second.
About the schedules
The MTU-TXC calculates each schedule to begin at
00:00:00 UTC each day and repeat continuously. For
