158
Extending Transmission over the Distance
When the transmission signals between the RS-485 communications become weak over the
distance, switch on the Terminal Resistance Switches to maintain the signals. Three
conditions below illustrate how the Terminal Resistance Switches should be switched on.
1. Multiple pieces of GV-I/O Box 8 are connected with the PC through one single
RS-485 cable.
After you connect multiple pieces of GV-I/O Box 8 with the PC, only switch on the
Terminal Resistance Switches in the first and last connected pieces of GV-I/O Box 8.
1
ON
1
ON
1
ON
Figure 2-41
2. Multiple pieces of GV-I/O Box 8 are connected with the PC through a RS-485 /
RS-232 conversion device.
After you connect multiple pieces of GV-I/O Box 8 with the PC through a RS-485 / RS-
232 conversion device, such as GV-NET/IO Card and GV-Hub, insert a Terminal
Resistor in the conversion device and switch on the Terminal Resistance Switch of the
last connected GV-I/O Box 8.
ON
ON
Figure 2-42
