Guralp Systems CMG-CD24 - Manual (Page 95)

Operator's Guide
The diode between pins A and R is important, because if two digitisers
generate a trigger simultaneously, their power supplies will both be
connected via the internal relay contacts to the common trigger line on
pins V, and hence connected together. This can cause considerable
current flow with consequent risk of fire, as well as severe damage to
equipment and cables.
In the case where a single power supply is used to power all of the
equipment, this is not an issue and pin A should be connected directly
to pin R on all units.
The more common case, where each unit has it's own power supply, is
shown above. Please note that all the power supply's ground terminals
will be connected together: they must, therefore, have floating outputs
or grounded negative terminals.
7.2.5 Combining CD24 and DM24 digitisers in a single array
The trigger inputs of a CMG-DM24 digitiser are slightly different to
those on a CD24: the return pin on the DMG-DM24 is connected
internally to the power supply ground (it is isolated on the CD24).
When building mixed arrays of CD24s and DM24s (or digital
instruments containing them), extra care should be taken with the
interconnections. Please contact Güralp Systems Ltd. technical
support for advice.
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