Operating instructions

3 COMMUNICATION LINES AND CONNECTIONS
3.1 Video line and telemetry lines
TheDCT keyboard can be used to control a wide range of products, for both video control (video matrixes and
video multiplexers) and telemetry control (receivers or domes). It is therefore necessary to define the system
structure at the keyboard level so as to achieve efficient communication between the connected devices.
“ Video line” means the communication channel intended to control the video device; “ telemetry line” means
the two channels available for telemetry control.
We advice starting with the configuration of the single “ video line” and after that passing to the configuration
of the “ telemetry lines”.
3.2 RS485 and types of systems
The RS485 communication channels are 2-wire lines whose maximum length from end to end is 1200m.
Termination of the RS485 lines prevents signal reflection along the cable, and should be inserted in each of the
devices that forms the end of a connection.
Systems can be of different types, therefore the way of terminating the lines will also be different.
In the following diagrams, the devices requiring termination are indicated by the
#
# # #
# #
# #
# symbol.
Configuration Description Example
Star /
Single lines
For each connection between two devices
there should be a separate communication
line, with a maximum length of 1200m.
All devices should be terminated, because
each appliance is connected to the end of a
line.
Backbone A single line is used, and the transmitters
can be placed in any position along it. The
two ends of the line (keyboard K and
receiver R3 in the example) are terminated;
the other devices (R1 and R2) are not
terminated. The maximum length of the line
is 1200m.
The specifications for the RS485 standard
allow at least 32 devices to be connected
along the same line.
Configuration Description Example
Line with stub A certain number of stubs can be shunted
in parallel to the standard RS485 line, for
connection to other devices. The stubs are
not at the ends of the line, should not be
terminated and they should be very short in
length (of the order of a couple of metres).
The specifications for the RS485 standard
allow at least 32 devices to be connected
along the same line.
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