7700FR/7800FR MultiFrame
7800TR-32x24 Modular Tally Router
Revision 1.2 Page - 15
3.7 WET POWER
The 7800TR-32X24 has wet power sources that are available on the two D-Sub connectors on the rear
plate. They can be used to provide voltage to GPIs and GPOs. This allows the GPIO to be either
powered or unpowered depending on the requirements of the equipment that needs to be interfaced to
(see section 0). This wet power source is available on the WET+ and GND pins.
The tally router’s wet power is software-selectable between two sources:
+5V
The internal +5V power will be connected to WET+. The GND pins act as the
return (chassis ground).
+12V
The internal +12V power will be connected to WET+. The GND pins act as
the return (chassis ground).
Table 3-7: Wet Power Source Selections
The wet power source WET+ is protected by a 1.5 Amp polyfuse, no matter which voltage source is
selected. Care must be taken to limit the cumulative WET+ current draw out of the rear D-Sub
connectors to 1.5 Amps or less.
If more current than the maximum is drawn, to the WET voltage polyfuse will heat up and open. This
process happens very quickly if the current is high, but could take hours if the current is only a little
above the maximum. When the fault is removed the polyfuse will begin to cool and will eventually reset
on its own. Note that with some types of faults this heating/cooling (fault/reset) process can happen
repeatedly, causing a “strobing” effect on the WET power to the load.
After changing the wet power source, allow 30 seconds for the setting to save
before rebooting or removing power from the card.
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