The Z21 has no display and is controlled entirely via app; the ECoS 2 has a 7" touchscreen and 6 amperes. Both are DCC stations — but with fundamentally different designs.
The black Z21 (Roco/Fleischmann, art. 10820) and the ESU ECoS 2 (art. 50210 and 50220) are both solid DCC stations with RailCom cutout and extensive feedback options — but they are fundamentally different in design. The Z21 has no display of its own and is operated exclusively through an external app or throttle: the station itself is compact and sits quietly in your layout cabinet. The ECoS 2 has a built-in 7-inch TFT colour touchscreen (800×480 pixels) and is a completely standalone station — you can drive directly on it, operate turnouts and configure loco addresses without any external device.
Three other key differences drive the choice: the ECoS 2 delivers 6 amperes of track current (the Z21 only 3 A), the ECoS supports Selectrix and M4 (mfx-compatible) in addition to DCC and Motorola, and the Z21 has a built-in LocoNet bus while the ECoS does not as standard. Anyone wanting more track current, running Selectrix decoders or preferring an autonomous screen station looks at the ECoS. Anyone preferring app control, wanting LocoNet or R-BUS feedback and looking for a lower price chooses the Z21.
| Z21 black (art. 10820) | ESU ECoS 2 (50210 / 50220) | |
|---|---|---|
| Display / control | No display — app/external only | 7" TFT colour touchscreen, 800×480 |
| Protocols | DCC (14/28/128 steps) + MM I/II | DCC + MM (old/new) + Selectrix + M4 |
| mfx auto-registration | Not supported | Via M4 (mfx-compatible) |
| RailCom cutout | Yes, global detector built in | Yes, integrated global detector |
| RailCom to ModelRailPro | Yes (via R-BUS / CAN) | To be confirmed on a layout |
| Track current | 3 A (12–24 V adjustable) | 6 A continuous |
| Feedback buses | R-BUS (max. 160 blocks), CAN, LocoNet, X-BUS | ECoSlink (CAN), s88 (galvanically isolated), ECoSniffer |
| LocoNet built-in | Yes | Not supported |
| ModelRailPro connection | UDP 21105 (Z21 LAN) — works | TCP 15471 (ECoSnet) — to be confirmed on a layout |
| Guide price | ~€280–340 (indicative) | ~€450–600 (indicative) |
The black Z21 delivers 3 amperes of track current, adjustable between 12 and 24 V. It supports DCC (14, 28 or 128 speed steps) and Motorola MM I and II — useful if you also want to run older Märklin locos that only have a Motorola decoder. No mfx: that is the deliberate distinction from the Märklin CS line. A built-in RailCom global detector with cutout is present; RailCom feedback is transmitted via the CAN bus.
The bus configuration is notably complete for this price range: R-BUS (Roco Feedback Bus, maximum 160 feedback blocks via 10 modules × 16 inputs), LocoNet for LocoNet devices and detectors, X-BUS (3 connectors), Booster Bus and Sniffer Bus. Anyone wanting to integrate an existing LocoNet network has a direct option with the Z21 without extra adapters. ModelRailPro connects via the Z21 LAN protocol on UDP port 21105; default IP is 192.168.0.111.
The absence of a display on the station itself is deliberate: Roco delivers the Z21 as a layout infrastructure component operated through an app, or via throttles on X-BUS or LocoNet. For anyone already comfortable working with a tablet or smartphone, that is no disadvantage.
Guide price black Z21: approx. €280–340 (indicative; prices vary by dealer and timing).
The ECoS 2 is available as model 50210 (ECoS 2.1, partly discontinued/secondhand) and 50220 (ECoS 2.5, new at approx. €550–600). The defining feature is the 7-inch TFT colour touchscreen (800×480 pixels) that lets you operate the station completely independently: drive, switch turnouts, create locos, without an external app or throttle. At the same time the ECoS also supports external connections for additional control options.
Track current is 6 amperes continuous — comfortably sufficient for larger HO layouts without an external booster. Protocols: DCC (14/28/128 steps), Märklin Motorola (old and new, 14 or 27 steps), Selectrix and M4. M4 is ESU's name for the mfx-compatible drive protocol (see the section below). RailCom cutout is built in with an integrated global detector.
Feedback buses: ECoSlink (ESU's own CAN-based system bus for expansion modules), s88 (galvanically isolated, directly on the station) and ECoSniffer for older hardware. What the ECoS 2 does not have as standard: a LocoNet or XpressNet bus directly on its housing. Extension via an ECoSlink module is technically possible, but connecting LocoNet devices to ModelRailPro is not spec-confirmed and is to be confirmed on a layout.
ModelRailPro connects via TCP port 15471 (ECoSnet text protocol), default IP 192.168.0.5. Connection status: to be confirmed on a layout. RailCom feedback towards ModelRailPro via ECoSnet is also to be confirmed on a layout. See the ECoS hardware page for the current status.
Guide price ECoS 2: approx. €450–600 (indicative; 50210 secondhand or discontinued, 50220 new approx. €550–600).
M4 is the name ESU uses for the drive protocol that provides mfx interoperability. In practice: Märklin mfx decoders register automatically at the ESU ECoS (via M4) and are recognised as valid loco addresses. Conversely, ESU M4 decoders register automatically at a Märklin CS2 or CS3. ESU and Märklin describe this basic interoperability publicly, and basic driving plus automatic registration works broadly in practice.
There is however a limit: ESU and Märklin do not publish a joint open protocol document. Functions beyond the basic definition — such as extended sound pages, advanced function remapping and extended CV settings — fall outside the published joint specification. Those edge functions are to be confirmed on a layout. Anyone specifically needing full Märklin mfx+ functionality should also compare the Märklin CS3 — see Märklin CS3 vs ECoS for a direct comparison of both high-end stations.
Also considering the Märklin CS3 alongside the ECoS? Read Märklin CS3 vs ECoS. Want to compare the Z21 with a Märklin station? See Z21 vs Märklin CS3.
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