Specifications

SA Buses with Multiple Network Sensors
An SA bus supports up to four network sensors. Figure 12 shows an example of two SA buses, each with four
network sensors. To place multiple network sensors on the bus, three of the network sensors must be DIP switch
addressable.
Note: Do not mix RJ-style modular (phone) jack and screw terminal devices on the SA bus. Due to the permanent
internal SA bus EOL termination contained in FECs, FACs, IOMs, and VMAs, using both the phone jack and
terminal block effectively puts the EOL termination in the middle of the SA trunk, creating a star network
configuration. This configuration violates the RS-485 network wiring guidelines and can cause unpredictable
communication problems.
Some NS Series Network Sensors and NS Series Discharge Air Sensors models are DIP switch addressable.
Figure 12: SA Bus Example Showing Multiple Networks Sensors
30MS/TP Communications Bus Technical Bulletin