ABB TB840A 3BSE037760R1 Modulebus Cluster Modem

Product Overview

The ABB TB840A (3BSE021456R1) is a ModuleBus Modem that serves as a fiber optic interface to the Optical ModuleBus in S800 I/O systems. It enables redundant I/O configurations where each module connects to different Optical ModuleBus lines while sharing the same electrical ModuleBus, supporting up to 12 I/O modules per electrical cluster and up to 7 clusters via fiber optic.

Key Specifications

• Manufacturer: ABB
• Part Number: TB840A (3BSE021456R1)
• Product Type: ModuleBus Modem
• System: S800 I/O
• Function: Fiber optic interface to Optical ModuleBus
• Electrical ModuleBus: Up to 12 I/O modules
• Optical ModuleBus: Up to 7 clusters
• Cluster Address: Set by rotary switch on TU807/TU840/TU841/TU848/TU849 (range 1–7)
• Power Output: 24 V DC protected, isolated 5 V DC to cluster I/O modules
• Redundancy: Supported (each module on different Optical ModuleBus lines)
• Mounting: DIN rail via compatible termination unit

Applications

• Optical ModuleBus I/O clusters
• Redundant S800 I/O configurations
• Long-distance I/O distribution
• Electrical isolation between controller and field I/O

FAQ

Q: What is the difference between TB840 and TB840A?
A: TB840A is a hardware revision/update of TB840 with improved reliability. Functionally they are interchangeable.

Q: Which termination units are compatible with TB840A?
A: TU807 (single), TU840/TU848 (redundant with shared power), TU841/TU849 (non-redundant with individual power).

Q: Can TB840A be used without fiber optics?
A: TB840A requires fiber optic connection for the Optical ModuleBus. For electrical-only ModuleBus, use direct electrical connections without TB840A.

Installation Guide

1. Mount the compatible termination unit (TU840, TU841, TU848, or TU849) on DIN rail.
2. Install TB840A onto the termination unit.
3. Set cluster address (1–7) using the rotary switch on the termination unit.
4. Connect 24 V DC power to L+ and L- terminals.
5. Connect fiber optic cables to the Optical ModuleBus ports.
6. Attach up to 12 S800 I/O modules to the electrical ModuleBus.
7. Verify power supervision via SA/SB inputs for redundant supplies.

Selection Tips

• Use TB840A for optical ModuleBus applications requiring electrical isolation or long-distance I/O.
• For redundant I/O, pair with TU840 or TU848 termination units.
• Verify fiber type (plastic, HCS, or glass) and connector compatibility (Versatile Link or ST).
• Consider TB825/TB826 optical media converters for fiber type conversion.