Application Scenarios

In a Symphony Plus​ or AC 800M​ control cabinet, the ModuleBus connects multiple I/O modules (e.g., SPDSI14, SPAO321) on a backplane or rail. The TB807​ must be installed at the very end of the bus​ (after the last I/O module). Without it, high-speed digital signals “bounce” off the unterminated end, creating electrical noise that leads to intermittent “ModuleBus Fault” alarms and unstable I/O scanning.

 

Parameter

Main Parameters	Value/Description
Product Model​	ABB TB807​ (Ordering Code: 3BSE008538R1)
Manufacturer​	ABB
Product Category​	ModuleBus Passive Terminator (总线终端匹配器)
Internal Resistance​	120 Ω​ (typical, for impedance matching)
Power Requirement​	None​ (Fully passive, no external power)
Compatible Systems​	S800 I/O, AC 800M​ controller racks, Advant S100​
Interface​	21-pin ModuleBus connector (plugs into backplane/rail end)
Operating Temp.​	0 °C to +55 °C​ (industrial control cabinet environment)
Dimensions (W×H×D)​	~17 × 19 × 13 mm​ (extremely compact)

 

 

Technical Principles and Innovative Values

This component is critical for signal integrity in high-speed industrial networks.

• Innovation Point 1: Signal Integrity Guardian:​ The TB807 acts as an “electrical sponge” at the bus terminus. It absorbs signal energy that would otherwise reflect back onto the line, preventing Intersymbol Interference (ISI). This is non-negotiable for the deterministic timing required by DCS safety loops.
• Innovation Point 2: Zero-Configuration Reliability:​ As a purely passive resistor network, it has no firmware, no configuration DIP switches, and cannot “crash.” Its Mean Time Between Failures (MTBF) is effectively infinite, making it the most reliable component in the rack.
• Innovation Point 3: Space-Optimized Design:​ Its tiny form factor (~17mm wide) allows it to snap onto the DIN rail or plug into the backplane without consuming a valuable I/O module slot, preserving cabinet density.

 

Application Cases and Industry Value

A steel plant’s AC 800M rack experienced random communication resets on its S800 I/O modules. After weeks of troubleshooting cables and controllers, engineers discovered the TB807 terminator was missing​ from the end of the rail. Installing the TB807 immediately resolved the signal reflection issue, restoring stable communication and preventing costly production downtime caused by spurious trips.

Related Product Combination Solutions

The TB807 is the “end cap” of the ABB ModuleBus ecosystem:

• Bus Master:​ ABB AC 800M​ (PM860, PM861) or CI854​ communication interface – generates the ModuleBus signal.
• I/O Modules:​ S800 Series​ (e.g., SPDSI14, SPAO321, SD822) – the devices communicating on the bus.
• Backplane/Rail:​ TU810, TU830​ or DIN rail mounting base – the physical medium where the TB807 must be installed at the far end.
• Complementary Component:​ In some configurations, a TB808​ (fiber optic bus terminator) may be used for optical ModuleBus links.

 

Installation, Maintenance, and Full-Cycle Support

⚠️ Important Note:​ While the TB807 itself is low-voltage and passive, the rack it is installed in contains live controllers and power supplies. Always follow plant LOTO (Lock Out Tag Out) procedures​ before handling. Although the module is often hot-pluggable, removing it while the bus is active will cause a communication fault on the entire downstream segment.