Installation & Service Manual
99
The output relays are the same hardware but the GPI is being driven by the GPI output
software and the relay tally is driven by the Relay Tally system software. Relay tally
connections can be used to trigger GPIs on external devices.
GPI Inputs
The purpose of the GPI In pins is to provide a stimulus from the external devices to the
switcher. A simple connection of two pins activates the corresponding input. An external
relay contact or an open-collector output can be employed.
Since the circuit ground is led out of the device, cabling should be shielded for this kind of
control. Non-shielded cables may cause EMC and/or ESD problems.
To activate a GPI In you must provide switch closure between a particular GPI In pin and its
common (1 or 20). Pins 1 and 20 of each connector are connected to ground. For
applications that span across more than one connector, only one ground (common)
connection is required.
The following diagram has the GV K-Frame X GPI inputs on the left.
+ 3.3 V
GPI IN 1
Opto Isolator
(1 of 4)
Ground and
Chassis
User Equipment Video Processor Frame
GPI Input Connections (Typical 1 of 4 Connections)
Relay Tally/GPI Outputs
Relay Tally and GPI Outputs are arranged in groups of four. Each group has its own common
connection. These commons can all be tied together, forming one common bus for all the
outputs. Alternatively, multiple smaller commons can be constructed to interface with
systems that need isolated common connections. This common or isolated bus scheme can
extend across multiple connectors. For example, a situation may require two isolated
common buses, half of the commons form the first common bus and the other half form
the second common bus.
22
20
CAUTION: When connecting to an open-collector output, there is no
ground potential isolation between the Video Processor
Frame and controlling devices.
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