Super Systems 20Q - Manual (Page 20)

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to the ” B ” terminal for a binary 0 (SPACE or ON).
4) The EIA standard establishes that by RS-485 interface it is possible
to connect up to 30 devices with one remote master unit.
The serial interface of these instruments is based on “High
input impedance” transceivers; this solution allows you to
connect up to 127 devices (based on the same transceiver
type) with one remote master unit.
21
20
COMMON
22
B'/B B/B'
A/A' A'/A
M
A
S
T
E
R
I
N
S
T
R
U
M
E
N
T
F) SERIAL INTERFACE F) SERIAL INTERFACE F) SERIAL INTERFACE F) SERIAL INTERFACE F) SERIAL INTERFACE
RS-485 interface allows you to connect up to 30 devices with
one remote master unit.
Fig. 17 - RS-485 WIRING
NOTES
NOTES NOTES NOTES NOTES:
1) The cable length must not exceed 1.5 km at 9600 BAUD.
2) This serial interface is isolated.
3) The following report describes the signal sense of the voltage
appearing across the interconnection cable as defined by
EIA for RS-485.
a) The ” A ” terminal of the generator shall be negative with respect
to the ” B ” terminal for a binary 1 (MARK or OFF) state.
b) The ” A ” terminal of the generator shall be positive with respect
mkc-ssi.pmd 06/07/2004, 12.19 16