Digital Communications Interfaces ________________________________________________________
RF-MCGARDPRO
Hubbell Power Systems, Inc.
–
RFL™
Products
July 1, 2022
©2022 Hubbell Incorporated
7-1
Digital Communications Interfaces
The Base System provides one RS-449/X.21/V.35 or G.703 64 kbps communication interface
mounted on the Power Supply I/O. Additional interfaces can be added as required, and as space
in the chassis allows. The 6U chassis can house an additional 7 communication interfaces, for a
total of 8. The 3U chassis can house an additional 4 communication interfaces, for a total of 5.
Both 3U and 6U chassis can have a maximum of 2 T1/E1 modules installed.
The digital communication interfaces are mounted from the rear of the chassis. See section
The communications interface connectors are located on the top half of the 6U chassis or on the
right side of the 3U chassis. The remaining half of the board can be equipped with a set of six
inputs, solid state outputs or relay outputs.
7.1
Digital Communications Function
The main function of the digital communications interface is to carry the digital teleprotection
data from the digital teleprotection module. In addition, digital communications interfaces can be
used to carry service channel data and can be used as multiplexed auxiliary channels.
Service channels
The service channel is a feature that provides access to a remote unit through the digital
communications interface connection. The GARD is capable of two independent service
channels, allowing access to two remote units. Each service channel consumes a 64kbps
timeslot of the digital interface. See
for the rules on creating Service Channels.
Auxiliary Channels
Auxiliary channels are used to multiplex local data from external equipment, such as a
protective relay, onto the primary GARD-to-GARD communications interface. If set to
“Aux-channel”, the module becomes an available timeslot function, that can be assigned to
another communications interface in the Timeslots > Bus 1 or Timeslots > Bus 2
configuration page. Auxiliary channels can only operate at 64 kbps. See section
more information on the timeslot configuration.
