The MOD-MUX enclosure is shown below. The module plugs into an industry standard 11 pin relay base. This base is normally clipped onto a DIN rail. Field wiring is on the front of the module via a separate plug in connector.

In most cases, MOD-MUX modules will be installed in an enclosure along with other devices which generate electromagnetic radiation. Examples of these devices are relays and contactors, transformers, motor controllers etc. This electromagnetic radiation can induce electrical noise into both power and signal lines, as well as direct radiation into the module causing negative effects on the system. Appropriate grounding, shielding and other protective steps should be taken at the installation stage to prevent these effects. These protective steps include control cabinet grounding, module grounding, cable shield grounding, protective elements for electromagnetic switching devices, correct wiring as well as consideration of cable types and their cross sections.

Transmission line effects often present a problem on data communication networks. These problems include reflections and signal attenuation.

To eliminate the presence of reflections from the end of the cable, the cable must be terminated at both ends with a resistor across the line equal to its characteristic impedance. Both ends must be terminated since the direction of propagation is bidirectional. In the case of an RS485 twisted pair cable this termination is typically 120 ohms.

Some of the MOD-MUX modules have built in termination resistors which are connected to the network by linking connections on the 11 pin relay base as shown in the diagram below. Note that only the modules at the end of the network should have the terminations linked onto the network.

The MOD-MUX I/O modules have a built in watchdog circuit which is used to monitor the microprocessor. The POWER LED flashing at ± 1 second intervals indicates that the microprocessor is faulty and must be repaired.