Communication Line And Connections; Video Line; Rs485 And System Types - Videotec DCK Manuel D'instructions

3 Communi cation line and connections

3.1 Video line

The DCK keyboard can be used to control a wide range of products. It is therefore necessary to define the
system structure at the keyboard level to achieve efficient communication between the connected devices.
"Video line" means the communication channel intended to control the video devices.
3.2 RS485 an d system types
The RS485 communication channels are 2-wire lines whose maximum length from end to end is 1200m.
The termination of the RS483 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 diagrams shown below, the devices requiring termination are indicated by the # symbol.
These are general schemes and they're not necessarily used for the DCK keyboard.
Setup
Star /
Single lines
Backbone
Line with stub
Devices in
chain
Description
For each connection between two
devices there should be a separate
communication line, with a maximum
length of 1200m.
All devices should be terminated, since
each device is connected to an end of
the line
A single line is
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
terminated. The maximum length of the
line is 1200m.
The specifications
standard allow at least 32 devices to be
connected along the same line.
A certain number of stubs can be
shunted in parallel to the normal RS485
line, for connection to other devices.
Since the stubs are not at the ends of
the line, they should not be terminated
and they should be very short in length
(of the order of a couple of metres).
The specifications
standard allow at least 32 devices to be
connected along the same line.
a The devices are connected in pairs
using single lines. These should be
terminated at the ends. This type of
setup can only be made when the
devices have a
(reception) and output (transmission)
channel, like the Videotec DTRX1 and
DTRX3 receivers.
Example
used, and the
R2) are not
for the RS485
for the RS485
separate input
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