Videotec DCTEL - Manual (Page 35)

Page 11 MNVCDCBD01_0442
The receivers are able to regenerate the received signal internally and re-transmit it along a new
communication line to the next receiver. Each of the three line sections (L1, L2, L3) is considered independent
connects only two devices point-to-point, each with the load inserted, and has a maximum length of 1200
metres. The distance between keyboard and receiver R3 may reach a maximum of 3600 m (1200 m between
the keyboard and receiver R1, 1200 m between receiver R1 and receiver R2, and another 1200 m between
receiver R2 and receiver R3, for a total of 3600 m).
NB: receivers with an address that is greater than 16 cannot be controlled by the DCTEL keyboard.
6.4.2 More than one keyboard and receiver per line (multi-point connection)
This type of connection allows one or more keyboards (even different types from DCTEL: DCJ for example) to
control one or more receivers arranged in the same line (multi-point connection).
All receivers connected to the same line should use the same, RS485, communication protocol.
For each line, the following observations are valid:
• only one of the keyboards (the one at an 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.
• each keyboard should have a different address from the others
• each receiver should have a different address from the others (between 1 and 16)
The ends (Keyboard K1- Receiver R3) should have the termination resistance inserted. Receivers R1, R2 and
the keyboard K2 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), a failure of one of the devices will not affect the other
receivers.