Videotec EXDTRX User Manual

Page 15

EN - English - I

nstruc

tions manual

Terminals RX-485A and RX-485B which have the load
inserted, should be connected to terminals TX-485A
and TX-485B respectively of the preceding unit,
which also have the load inserted:

RS485

TX-

RX-

RS485

TX-

RX-

RS485

TX-

RX-

From previous

receiver

To next

receiver

Fig. 10

For the connection in question (point-
to-point) faulty operation of one of the
receivers will switch off all the devices in
cascade.

6.2.11 More than one receiver per line,
connection with twisted pair cable
(multipoint connection)

All receivers connected to the same line should use
the same communication protocol RS485.
For each of the lines the following remarks are valid:
• Only one of the keyboards (that at one end of the

line) has the load inserted;

• Only one of the receivers (at the other end of the

line) has the load inserted;

• The total length of the line should not exceed

1200m.

6.2.10 Connecting more than one receiver
in cascade (point-to-point connection)

The receivers are able to regenerate the received
signal internally and retransmit it along a new
communication line to the subsequent receiver. Each
of the three sections of line (L1, L2, L3) is considered
independent, and connects only two devices
point-to-point, each with inserted load, over a
maximum distance of 1200m. The distance between
the keyboard and receiver D can therefore be up
to 3600m (1200m between keyboard and receiver
B, 1200m between receiver B and receiver C, and a
further 1200m between receiver C and receiver D, for
a total of 3600m).

EXPT

DCT

EXPT

EXDTRX3

EXDTRX324

EXDTRX3

EXDTRX324

EXDTRX3

EXDTRX324

Fig. 09

The connection between the keyboard and the first
receiver must be carried out as illustrated in the
diagram in Fig. 08, page 12.