Meinberg TCR LANTIME User Manual
Page 21
Input for modulated codes
Modulated codes must be applied to the on board SMB Connector. An automatic
gain control allows decoding of codes within an amplitude range from abt. 600 mVpp
up to 8 Vpp. To allow adaption of different time code generators, the boards input
impedance can be selected by an on board jumper.
Input impedance
The IRIG-specification does not define values for the output impedance of
generators or the input impedance of receivers. This fact led to incompatibility of
some modules, because the manufacturers could choose the impedances freely. For
example: if the output impedance of the generator is high and the input impedance of
the receiver low, the signal level at the receiver input might be too low for correct
decoding. Therefore the board TCR510 provides a jumper to select the impedance
(50
Ω
, 600
Ω
or 5 k
Ω)
of the input for modulated codes ( SMB ) to comply with the
requirements of several systems.
Meinberg IRIG-generators have an output impedance of 50
Ω
, to build a matched
transmission system when using a coaxial cable. If such a generator is used to
synchronize TCR510, the input impedance has to be set to 50
Ω
accordingly (default
on delivery).
In addition to the telegram, the AFNOR-code defines the input/output impedances
also. If TCR510 is synchronized by this code, an input impedance 600
Ω
of must be
set.
The setting „5 k
Ω
“ may be necessary if the generator has a high output impedance
(see specifications of manufacturer). The driver software shows a bar chart for
evaluation of the signal level at the receiver input.
The following detail of the placeplan of TCR510 shows the possible jumper setting
with the related input impedance:
JP1 in Position 1 - 50
JP1 in Position 2 - 600
JP1 offen - ca. 5 k
Ω
Ω
Ω
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