Specifications

Note: The majority of properly grounded MS/TP applications do not require soft ground connections, but you should
assess the potential interference that your application may encounter (before you install the bus). It is more
efficient to prepare for soft ground connections when making the bus terminations at the initial installation
than to return and do it later.
Soft ground connections should be made within 2 inches of the bus terminations of any bus device that experiences
frequent offline occurrences resulting from high ambient inductive or RF interference (Figure 15).
Figure 15: Applying a Soft Ground Connection to an FC Bus
RJ-Style Modular Jack and Cables for SA Bus
The 6-pin modular jack SA bus connection (Figure 16) is a straight-through (not a crossover) connection and that
uses a 6-wire connector cable (with 6-pin RJ-style modular jacks) to connect SA devices to network sensors, DIS1710
Local Controller Display, and the VMA Balancing Sensor. On the 6-wire cable, two wires are used for network
communication, two wires for network sensor power, and two wires supply 15 VDC (200 mA maximum) power to
the devices connected to the sensor.
The Wireless Commissioning Converter (MS-BTCVT-1) is also connected (temporarily) to the SA bus modular jack
to commission the controller.
The cable connected to the SA bus 6-pin modular jack is a straight-through cable and cannot exceed 30 m (100 ft).
Do not use crossover cables on the SA bus.
The SA bus 6-pin modular jack supports only one device and no other SA device may be daisy-chained to the port.
Important: Failure to adhere to these wiring details may cause your network sensor to function incorrectly. You
are not able to connect to the system using the Wireless Commissioning Converter, the Handheld
Variable-Air-Volume (VAV) Balancing Sensor, nor can you expand the system with future offerings.
Every MS/TP device (except the NAE55) has at least one 6-pin modular jack. Modular jacks on the network sensors
allow you to connect a Wireless Commissioning Converter (MS-BTCVT-1) or VMA Balancing Sensor. Figure 16
shows the SA Bus modular jack pinout.
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.
38MS/TP Communications Bus Technical Bulletin