Videotec DTMRX2 - Manual (Page 40)

Page 14 MNVCDTMRX2_0351
7.8.1 Connecting more than one receiver in cascade (point-to-point connection)
The DTMRX2 (DTMRX224) receivers are able to regenerate the received signal internally and retransmit it on a
new communication line to the next receiver. Each of the three stages of the line (L1, L2, L3) is considered
independent, and connects only two devices point-to-point, each with the load inserted, over a maximum
distance of 1200 metres. The distance between keyboard K1 and receiver R3 may therefore reach 3600m
(1200 m between keyboard K1 and receiver R1, 1200 m between receiver R1 and R2, and a further 1200 m
between receiver R2 and receiver R3, for a total of 3600 m).
Note: Terminals RX485A and RX485B, which have the load inserted, should be connected to terminals
TX485A and TX485B respectively on the previous unit, and these also have the load inserted. Terminals
TX485A and TX485B with the load inserted should be connected to terminals RX485A and RX485B
respectively on the subsequent unit (always with the load inserted):
N.B,: For the connection under consideration (point-to-point), faulty operation of one of the receivers implies
that the devices in cascade will be cut off.
7.8.2 More than one receiver per line, connection with twisted pair (multi-point connection)
All receivers connected to the same line should use the same communication protocol, RS485.
For each of the lines, the following observations should be taken into consideration:
• only one of the keyboards (the one at an end of the line) has the load inserted
• only one of the receivers (the one at the other end of the line) has the load inserted.
• the total length of the line should not exceed 1200m.
Line A of keyboard K1 has been used for communication with the telemetry. The ends (Keyboard K1 - Receiver
R3) should have the termination resistance inserted. Receivers R1, R2, should not have the termination
resistance inserted. The maximum length of the line, from end to end (from keyboard K1 to receiver R3), is
1200 metres.
N.B.: For the connection in question (multi-point), faulty operation of one of the devices does not influence the
other receivers.
From previous
receiver To subsequent
receiver