Manual

© Mass Electronics Pty Ltd 2007
Innotech Device Network Cabling Installation Instructions
Edition 3.0 dated 05.12.2013
Page 18
There are a number of rules that apply to the comms connection of a primary network.
Some of these are explained in detail in Chapter 1 of this manual.
Primary network rules:
• The screen must be continuous
• Only one point earthed on the screen
• Even if a network has a number of devices with a so earth, one hard earth is still required on that
network
• The Net and Global networks should have the same length cable run and path
• If a repeater is installed, each side of that repeater is a separate network and each requires a
bonded earth connection on the screen
• Using isolated devices, devices with isolated comms cards or using an isolated MPI does not alter
any of these rules
• There are no End of Line termination (EOL) requirements on the primary network
2-1 Continuous Screen
The screen on a primary network needs to be continuous. That means it remains unbroken along its
entire length. As there is one ‘S’ terminal on a typical primary network device both the global and net
screens are to be connected to this tie terminal.
G+ S N+G- N-
Figure 2-1: Typical Screen Connections
GLB Comms
NET Comms

When there is more than one connection point to earth the screen becomes a conductor and no longer performs
correctly. Care should be taken to ensure only one bonded earth point is ever connected on a primary network.
Refer to Chapter 2-6 for details on use of a Repeater in a primary network.
NOTE
G+ S N+G- N-
G+ S N+G- N- G+ S N+G- N-
Device Device Device

Figure 2-2: Earth Connection