The ABB LK/S 4.3 Line Coupler (order code 2CDG110310R0011) is the current MDRC line / area / segment coupler with KNX Data Secure and proxy function. It structures medium and large installations by coupling lines to main lines, main lines to area lines, or acting as a repeater with electrical isolation between TP segments — filtering group telegrams according to the ETS topology and filter table.

Compared with LK/S4.2, the 4.3 generation adds Secure-oriented commissioning and proxy behaviour documented in the ABB product manual and the dedicated LK/S 4.3 ETS application. Always load the LK/S 4.3 application on this hardware — do not reuse LK/S 4.2 parameter sets. For long-distance isolation via fibre instead of copper coupling, see LL/S1.1.

Place the coupler at the boundary between segments, provide correct bus power on each side, and verify filter / Secure settings before going live. Physical form is compact MDRC (2 MW class) for DIN-rail installation next to SV/S or SU/S supplies.

Key Features — Secure Topology Coupler

• Line / area / segment coupler: Topology structuring with galvanic isolation between segments.
• KNX Data Secure: Secure telegram handling per ABB/ETS configuration.
• Proxy function: Modern coupler proxy behaviour as described in ABB LK/S 4.3 docs.
• Repeater mode: Extends TP segment reach while keeping isolation.
• Filter tables: Passes only the group telegrams required by the project topology.
• ETS application LK/S 4.3 only: Do not commission with LK/S 4.2 software.

At a Glance

Specification	Detail
Product type	Line Coupler Secure with proxy, MDRC
Order code	LK/S4.3 (2CDG110310R0011)
Functions	Line / area / segment coupler, repeater, Data Secure, proxy
Predecessor	LK/S4.2 (different ETS application)
Mounting	35 mm DIN rail, MDRC (2 MW class)
Isolation	Electrical isolation between coupled bus segments

Filter behaviour, Secure commissioning and wiring are in the ABB product manual under Downloads.