Meinberg TCG510 - Manual (Page 4)

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Abstract
The transmission of coded timing signals began to take on widespread importance in
the early 1950´s. Especially the US missile and space programs were the forces behind
the development of these time codes, which were used for the correlation of data. The
definition of time code formats was completely arbitrary and left to the individual ideas of
each design engineer. Hundreds of different time codes were formed, some of which
were standardized by the "Inter Range Instrumantation Group" (IRIG) in the early 60´s.
Except these "IRIG Time Codes" other formats, like NASA36, XR3 or 2137, are still
in use. The board TGV510 however generates the IRIG-A or IRIG-B, AFNOR NFS
87-500 code as well as IEEE1344 code which is an IRIG-B123 coded extended by
information for time zone, leap second and date. If desired other formats are available.
Principle of Operation
The Board TGV510 was designed for the generation and distribution of IRIG,
AFNOR and IEEE1344 standard time codes. Particularly it is intended for operation
with the Meinberg GPS radio clocks GPS161, GPS163 and GPS167 as well as the
DCF77 correlation receiver PZF509. Apart from the digitally generated amplitude-
modulated code, TGV510 also provides the unmodulated DC-Level shift code. The
modulated timecode is available at five outputs (4 x BNC- or SMB-connector, 1 x VG-
connector). The modulated sine wave carrier and the boards internal time pattern are
derived from the radio clocks disciplined oscillator. For special applications, the board
can be equipped with a freewheeling oscillator ( OCXO or TCXO ). Signals needed for
operation are a synchronuos pulse per second signal (PPS), a serial time string at RS232
level, and a 10MHz reference clock as mentioned above. After reading the serial
timestring the IRIG code is phase-locked to the precise pulse per second signal coming
from the radio clock. TCR510 uses a special software regulation to stabilize the internal
time pattern. Bounces of the external PPS signal less than +/- 300µs are corrected in steps
of 1µs per second. In AFNOR-Mode the output signal level is automatically set accor-
ding to French-Std. NFS-87500.