Meinberg TCR510PCI, Operating Instructions Manual

Page: 13 / 20

13
Input impedance
The IRIG-specification doesn’t define values for the output impedance of generators
or the input impedance of receivers. This fact led to incompatibility of some modu-
les, 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 TCR510PCI contains a jumper to select the impedance (50
Ω
,
600
Ω
or 5 k
Ω)
of the input for modulated codes (BNC) to comply with the
requirements of several systems.
Meinberg IRIG-generators have an output impedance of 50
Ω Ω Ω Ω Ω
, to build a matched
transmission system when using a coaxial cable. If such a generator is used to synchroni-
ze TCR510PCI, 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 TCR510PCI is synchronized by this code, an input impedance of 600
Ω Ω
Ω Ω Ω
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 TCR510PCI shows the possible jumper
setting with the related input impedance: