# Commax intercom: how to modernize it without replacing the street panel > Which Commax system your building has, how it's actually wired (3 common wires + 1 per apartment), why the same part always fails, and what can be modernized while keeping the existing street panel. - Published: 2026-08-19 - Canonical (HTML): https://doorlink.com.ar/en/blog/modernizar-portero-commax - Versión en español: https://doorlink.com.ar/blog/modernizar-portero-commax.md --- Commax is probably the most common intercom brand in Argentine buildings, and also one of the most misunderstood when it comes to modernizing. The classic misconception: believing that routing calls to residents' phones means tearing out the street panel. On most Commax building systems it doesn't, and the reason lies in how the system is wired. This article is Commax-specific. If you're still at the diagnostic stage — you don't yet know what broke — start with [my building intercom isn't working](https://doorlink.com.ar/en/blog/portero-electrico-no-funciona), which covers the five typical faults and what repairs cost. ## Which Commax system does your building have? The first thing is to separate single-family units from building systems, because they look alike and aren't the same thing. The DP-2S, for instance, is a house intercom: two wires for the call, two more for the lock, one handset. That's not what you have in an apartment building. For buildings, Commax Argentina organizes its catalogue into four multi-family lines: **Modum Audio**, **Botonera Simple** (single button column), **Doble botonera** (double button column) and **Doorking**, 21 products in total. The ones you'll find in most buildings of a certain age are the metal button panels: - **DR-nUM** (single column): aluminium panel, versions with 2, 4, 6 and 8 push-buttons, DC 12V 1A power supply. - **DR-nAM** (double column): cast aluminium for flush mounting, versions from 2 to 16 push-buttons, same power supply. Inside the apartments, the usual handset is the **DP-SS**, which Commax describes as the "telephone for the entire multi-family line" — the same handset serves both the AM and UM lines. It's a two-way full-duplex audio unit, 72 x 215 x 38 mm, supporting cable runs up to 200 metres. The practical detail: the number in the model name (2UM, 12AM) is the count of push-buttons on the panel, not the number of floors. To find out what you have, look at the street panel and count the buttons; the model is usually printed on the panel itself or on the power supply. ## How is a Commax building system wired? This is the point everything else follows from. Commax's own specification for the DR-nUM and DR-nAM panels reads, verbatim: > Cableado: 3 cables en común / +1 por pulsador / Luz LED / + 2 Cerr Translated: there are **three common conductors running through the whole building**, plus **one individual conductor per apartment**, plus the panel's LED wire and a pair for the electric lock. This is the topology the trade calls "n+1": everything shared travels on a handful of wires, and each unit is distinguished by its own dedicated cable. ![How a Commax building intercom is wired: three common conductors plus one individual wire per apartment run from the DR-nUM or DR-nAM street panel to each DP-SS handset. The individual wires are buried in the wall and are what breaks most; the panel is the most robust part, and that is where the retrofit module connects.](https://doorlink.com.ar/blog/commax-cableado-en.svg) One frequent confusion is worth clearing up, because it causes arguments when quotes come in. The panel's datasheet says "3 common wires", but the DP-SS handset's datasheet says "4-wire cabling". They don't contradict each other — they're counting different things. At the panel's terminal block there are three commons; at an apartment's handset those three arrive plus that unit's individual conductor, so four. That's why the same system gets described as 3+n or as 4-wire depending on who's writing, and why whoever works on it should look at the actual installation rather than trust the paperwork. ## Why does the same part always break? Because the topology concentrates the fragility in two places, and neither of them is the street panel. The first is the **individual conductors**. There are only three commons; the individual ones are one per apartment, and they run up through conduits buried in the wall, with decades on them. When one apartment fails and everyone else is fine, it's almost always that run. It's also the most expensive and most invasive repair, because the cable is inside the wall. The second is the **handsets**. The DP-SS is a mechanical device with a hook, a speaker and a microphone, mounted in the kitchen, used several times a day for years. They wear out. The street panel, by contrast, is usually the most robust part of the whole system: cast aluminium, no moving parts except the buttons. It's the most visible piece and the one everybody proposes replacing first, and it's usually the one that least needs replacing. ## Can a Commax be modernized without replacing the panel? Yes — that's precisely what a retrofit does. The module connects **at the street panel's terminal block**, which is where the three commons and every individual conductor terminate. From there the call goes out over the internet to each resident's phone instead of travelling up the cable to the handset. That has a concrete consequence for the most annoying case: if the problem was one apartment's broken individual conductor, that run simply **stops being used**. No opening walls, no pulling new conduit, and nothing changes for the neighbours. Nothing changes for the visitor either: they press the same button on the same panel as always. No phone, no mobile data, no QR code to scan — a difference that matters more than it sounds, and one covered in [physical button or QR code](https://doorlink.com.ar/en/blog/boton-fisico-vs-porteros-qr). Now the honest caveat: **"Commax" is not a single specification**. Between a twenty-year-old DR-2UM, a DR-16AM and a Modum Audio there are real differences, and on top of that many Argentine installations have been modified over the years by different technicians. DoorLink works with the 4+n and 5+n wire intercom systems used by most Argentine buildings, Commax among them, but the only serious way to confirm it for your building is to look at the installation. If you're not sure what you have, that gets verified before quoting, not after. ## Does the existing Commax handset keep working? Yes. In a retrofit over an existing intercom the original handset is kept, so both paths coexist: whoever wants to answer on the DP-SS in the kitchen carries on doing that, and whoever prefers their phone answers there. This is what defuses the most common objection at the owners' meeting — "the older residents will never adapt" — because nobody is forced to change their habits. That subject is covered with data in [is a smart intercom easy for older adults to use?](https://doorlink.com.ar/en/blog/portero-inteligente-adultos-mayores). ## What if the Commax panel is already destroyed? It happens, especially with vandalism or a stolen panel. In that case there's no retrofitting something that isn't there: a new street panel gets installed. Rewiring the building still isn't necessary, because the commons and individual conductors already run through it and stay in use. The difference is one of cost and building work, and for that the full comparison is in [replace or modernize the intercom](https://doorlink.com.ar/en/blog/reemplazar-o-modernizar-portero). ## What does modernizing a Commax cost? DoorLink installation is a one-time cost, with hardware included, and the monthly per-apartment service is billed to the building's HOA. The comparison that matters isn't against zero, but against what the building already spends: the maintenance retainer, the one-off repairs and the after-hours surcharges. That arithmetic, split per apartment, is worked out in [what a smart intercom costs a building](https://doorlink.com.ar/en/blog/costo-portero-inteligente-consorcio), and the exact number for your building — without relying on a conversion inflation will make stale — takes a minute in the [calculator](https://doorlink.com.ar/en/calculator). ## What should you check before deciding? Five concrete things, in this order: 1. **Which panel model is installed.** Count the push-buttons and look for the model printed on the panel or the power supply. 2. **How it's actually wired.** Three commons plus one per apartment is what to expect, but an old installation may have been modified. This gets inspected, not assumed. 3. **Whether the fault affects the whole building or one unit.** It determines whether the problem is in the shared parts or in an individual conductor, and it changes the quote completely. 4. **What keeps working when the internet goes down.** Ask any vendor, ourselves included. 5. **What happens when tenants move in and out.** In a building with turnover, that's administrative work every month. The full eleven questions to put to any vendor before taking a quote to the owners' meeting are in [the building manager's checklist](https://doorlink.com.ar/en/blog/como-elegir-portero-inteligente-administrador). And if what's missing is understanding how the decision gets approved — what majority the Civil and Commercial Code requires, how it's split across expensas — that's in [a smart intercom for the building](https://doorlink.com.ar/en/blog/portero-inteligente-para-consorcio). If you'd like us to check which Commax system your building has before talking numbers, [get in touch](#contact) and we'll take a look.