Satec System 295 Installation And Operation Manual page 37

Table 2-2 RS-422/RS-485 pinout
Pin Name
1 0V
6 TXD+
7 RXD+
8 TXD -
9 RXD -
For RS-485 communications, connect together pins 6-7 (TXD+ and RXD+), and pins 8-9
(TXD- and RXD-).
Receive/Transmit Indicators
The PM295 has two LED indicators, showing activity on the serial port lines. They
are located to the left of the communications connector. The left LED is connected
to the receive line and flashes when the instrument is receiving data, and the right
LED is connected to the transmit line and flashes when the instrument is
transmitting data.
Cable Connections
For the cable drawings, refer to Appendices D, E and F.
For RS-422/RS-485 balanced data transmission, a shielded, twisted pair cable
should be used for each communication link. To minimize reflections and reduce
cross talk, it is recommended to terminate the ends of lines with the termination
resistor of 200-500 Ω.
For RS-232 connections, a flat cable can be used.
The conductor size of the 2 wires shall be 24 AWG or larger with wire resistance
not exceeding 30 Ω per 1000 feet per conductor.
When lines are routed through an electrically noisy environment, input protection
against switching or lightening induced surge voltages may be required in addition to
line termination.
Installation
Function
Common
+ Transmit Data
+ Receive Data
- Transmit Data
- Receive Data
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