Application Scenarios:

A machine builder was commissioning a bottling line whose infeed conveyor sat roughly four metres from the main control cabinet, on the far side of an aisle that could not be crossed with a second fieldbus drop. Running 32 digital inputs and 12 valve outputs back to the main cabinet meant 60-plus metres of multicore cable, two junction boxes and a day and a half of terminations — and any later addition would mean pulling more copper through the same tray.

The fix was to keep the PROFIBUS coupler and the bulk of the I/O in the main cabinet, terminate that assembly with a bus extension end module, and start a second, short assembly next to the conveyor with the 750-628. One double-shielded Ethernet patch cable carried the entire internal bus across the gap. The field devices were wired locally into the second assembly, the terminating resistor switch on the 750-628​ was set to ON because it was the last coupler in the chain, and the PLC saw one continuous node with unchanged addressing. Cable cost and termination labour dropped sharply, and when the line was later extended with a reject station, a third assembly was simply daisy-chained from the 750-628‘s second RJ45 socket.

The same pattern solves a familiar set of pain points: control cabinets with no spare rail space, retrofit projects where additional I/O has to be placed on the machine rather than in the panel, distributed skids that must share one fieldbus address, and legacy nodes whose 64-module limit has been reached without adding another fieldbus station to the master configuration.

 

Parameter:

Main Parameters	Value/Description
Product Model	750-628​ (Bus Extension Coupler Module)
Manufacturer	WAGO Kontakttechnik GmbH & Co. KG, Minden, Germany
Product Category	System module — internal data bus extension coupler for WAGO-I/O-SYSTEM 750
Mating Module	Bus extension end module 750-627; one end module plus at least one 750-628​ form a working set
Bus Connection	2 × RJ45 socket (input + output) for cascading to further assemblies
Extension Depth	Up to 10 coupler modules = 11 partial nodes; up to 64 I/O modules per node (system total governed by the coupler/controller)
Distance Between Components	Max. 5 m between end/coupler or coupler/coupler modules (10 m with capable couplers/controllers, see manual); max. 70 m for the complete node — the figure that decides whether a machine can be split across bays
Transmission Medium	Shielded copper cable (Ethernet patch cable), 4 × 2 × 0.25 mm², twisted pair, double-shielded STP
Supply Voltage (System)	DC 24 V (−15% … +20%) via CAGE CLAMP® connection; input current max. 200 mA at 24 V; inrush 2.5 × continuous current; supply efficiency 76%
Current Budget	150 mA internal consumption (5 V system supply); 400 mA total available for downstream I/O modules — check this against the sum of the connected modules’ 5 V draw
Field-Side Supply	DC 24 V (−15% … +20%) via 3 power jumper contacts, max. 10 A per contact; 500 V isolation between system and supply/field
Diagnostics	2 LEDs for system and field-side supply voltage; 2 LEDs in the RJ45 input socket for fault-free communication; module bus status LEDs
Termination	Integrated matching resistor (terminating resistor) switch — only one may be ON in the whole system
Mechanical & Environmental	24 mm W × 100 mm H × 69.8 mm D (62.6 mm from DIN-rail upper edge), approx. 74.5 g, light grey PC / PA 6.6 housing, IP20, DIN-35 rail, pollution degree 2, 0 … 2000 m altitude
Operating Conditions	0 … +55 °C operating, −40 … +85 °C storage, 95% RH non-condensing, vibration 4 g per IEC 60068-2-6, shock 15 g per IEC 60068-2-27
Connection & Approvals	CAGE CLAMP®, 0.08 … 2.5 mm² / AWG 28 … 14, strip length 8 … 9 mm; CE, UL 508, EAC, KC, plus DNV and BSH marine approvals; EMC per EN 61000-6-2 / EN 61000-6-4

Note: some older WAGO documentation lists the width as 25 mm and the weight as approx. 170 g; the current data sheet gives 24 mm and 74.5 g. Verify against the rating label when planning tight rail layouts.

 

Technical Principles and Innovative Values:

Innovation Point 1 — Transparent extension with zero re-engineering:

The 750-628​ does not create a new fieldbus node. It regenerates and forwards the node’s internal data bus, so the fieldbus coupler/controller continues to see a single contiguous I/O assembly. Module order, address mapping, parameter data and process image are untouched. For a plant adding I/O to a validated process, this means no re-configuration of the PLC master, no GSD/EDS change, and no re-validation of the fieldbus configuration — a difference measured in engineering days rather than hours.

Innovation Point 2 — Ten-stage cascading turns one node into eleven physical locations:

Each 750-628​ provides an output socket for the next link, supporting up to 10 coupler modules and therefore 11 partial nodes over a total bus length of 70 m. This is what lets a single fieldbus address serve a main cabinet, a remote operator station, a conveyor section and a skid — instead of four separate drops, four addresses and four sets of spare parts.

Innovation Point 3 — Separate, isolated system and field supply per segment:

The 750-628​ allows the field-side 24 V and the internal electronics 24 V to be fed independently, with 500 V isolation between them. A short circuit or a noisy actuator supply on one machine section therefore does not drag down the logic supply of the rest of the node. The three power jumper contacts rated at 10 A each carry the field potential onward, so downstream assemblies can be fed from a local supply rather than through the bus.

Innovation Point 4 — Built-in terminating resistor and meaningful diagnostics:

Bus termination is handled by a switch on the 750-628​ itself, removing the external terminator, its wiring and the guesswork about where it belongs. The rule is strict — exactly one resistor ON across the whole system — and the module makes compliance visible rather than procedural. Two LEDs inside the RJ45 input socket confirm fault-free communication with the head coupler, and separate system/field supply LEDs turn a “node down” event into a two-second visual check instead of a laptop-and-cable investigation.

Innovation Point 5 — Fieldbus independence with 24 mm packaging:

Because the 750-628​ works on the internal bus, it is not tied to PROFIBUS, Modbus, CANopen, DeviceNet, PROFINET or EtherNet/IP — it sits behind whatever fieldbus coupler or controller the node already uses. At 24 mm it consumes barely more rail space than a standard 4-channel digital input module, and it can be mounted in any orientation, which matters in vertical marshalling cabinets and machine-mounted enclosures.