Instructions

Description of the SHDSL permanent line modem
104275_en_c00 PHOENIX CONTACT 1-7
1.5.2 RS-422
The RS-422 standard supports serial data transmission in full duplex mode between two de-
vices. In the case of the RS-422 interface, data can travel distances of up to 1200 m. Trans-
mission speeds of up to 2000 kbps are possible.
The RS-422 interface is operated with at least two data channels: transmit (T) and receive
(R).
Figure 1-3 RS-422 interface
Termination resistors (100 ... 200 ohms) are provided at the inputs of the receiver. These
resistors prevent reflections on the transmission cable and increase transmission reliability.
In addition, to ensure reliable transmission the differential mode voltage between twisted
wire pairs is evaluated. Interference voltages in relation to ground are not taken into consid-
eration.
The signal level is defined as follows:
Data cables -0.3 V to -6 V for logic "1" The signal status is indicated
by the voltage between mea-
suring points (A) and (B).
+0.3 V to +6 V for logic "0"
Properties of RS-422
Standards ITU-T V.11/DIN 66259-3, TIA/EIA-422
Transmission speed 2000 kbps, maximum
Transmission length 1200 m, maximum (on the RS-422 side)
Method Voltage difference, twisted pair
Principle Full duplex, point-to-point, no multipoint connection
.For additional information, please refer to "Connecting the serial interface" on page 2-9.
T (A)
DTE DTE
R (A)
R (A)
T (A)
T (B)
R (B)
R (B)
T (B)