7 connecting the control unit, 8 connection with the rs485 line – Videotec DTMRX2 User Manual
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MNVCDTMRX2_0351
7.7 Connecting the control unit
The RJ11 connector present on the receiver (see J4 on page 8) is used for reception and transmission of digital
data in RS485 or RS232 thus allowing a rapid connection with the keyboards during any test stages, or for
connecting conversion interfaces that are available on the market (RS232-optic fibre).
For definitive connection with the keyboards, on the other hand, use the terminals present on the J5 terminal
board. We advise using RS485 mode which is able to reach a maximum distance of 1200 metres and
communication is immune to external interference. In COAX reception mode, on the other hand, it is possible to
reach a maximum distance of 350 metres from the control unit (via SMXXA series matrixes). Lastly, in RS232
reception mode it is possible to cover a maximum distance of 15 metres from the control unit (PC or DCS2 and
DCMT8 model keyboards).
7.8 Connection with the RS485 line
The DCJ, DCT, DCTEL keyboards and the DTMRX2 (DTMRX224) receiver can be connected directly by the
telephone cable supplied with the keyboard and using the RJ11 (J4) connector present on the circuit. For a
definitive connection between control unit and receiver, refer to the following procedure:
Keyboard – receiver connection
Connect the telemetry outlet of the keyboard to the RJ-JACK shunt box using the supplied telephone cable. Use
a twisted pair cable to connect the receiver terminals marked by screen printing RX485A and RX485B to the
RJ-JACK shunt box that has already been connected to the keyboard. Refer to the following diagram and the
table below to make a correct installation;
RS485 communication mode: Maximum distance 1200 metres.
DCJ, DCT, DCTEL, DCIR
(RJ11 A o B)
DTMRX2
DTMRX224
White TX-485A
--------
RX485A
Yellow TX-485B
--------
RX485B
Three possible system installations are illustrated below:
• Point-to-point connection (in cascade)
• Multi-point connection (in parallel)
• Mixed
connection
To the keyboard
telemetry
connector
Receiver
Terminal