Termination Resistor

The SG-785 CR is an optional signal conditioning module for RS-485 networks. It lets you set pull-high and pull-low biasing on the bus with switches, so the line can be held in a defined state without external components.A 15-step, switch-selectable termination resistor covering 65 to 560 ohm allows the correct load to be applied at the end of a long-distance RS-485 run. A red LED shows power status and a green LED shows when termination is active, so the module's state can be checked at a glance during commissioning.The CR suffix denotes the RoHS-compliant version. The module mounts on a DIN rail and operates from 10 to 30 VDC, with an operating temperature range of -25 °C to +75 °C.ApplicationsRS-485 signal pull-high/pull-low biasingTermination resistor setting for long-distance RS-485 communication

The tM-SG4 CR is an optional module for improving signal quality on RS-485 networks. It lets you set pull-high and pull-low bias resistors with switches, and select line termination from 15 steps without having to calculate a value by hand.Termination is only needed on longer runs. Where the network is under 100 metres, the module can usually be left out. On longer networks, termination resistors may be required at both ends of the bus. The most reliable way to choose the value is to examine the RS-485 signal on an oscilloscope: a clean square wave indicates a good impedance match, while distorted edges point to the need for termination at both ends.A red LED shows power and a green LED shows when termination is active. The module is DIN-rail mountable, has reverse polarity protection and is rated for operation from -25 °C to +75 °C.ApplicationsBiasing RS-485 networks with pull-high and pull-low resistorsTerminating RS-485 buses, particularly runs over 100 metresImproving communication reliability on RS-485 networks