An intercom can look like a simple device.

One handset talks to another. A gate station calls the house. A button opens a gate or door. From the client’s side, it should feel straightforward.

But when an intercom starts buzzing, humming, crackling or producing a strange background noise, the first instinct is often to blame the handset.

Sometimes the handset is faulty.

Often, it is not.

In real installations, especially on larger South African homes where low-voltage systems share busy ceilings, DB areas, gate routes and service ducts, intercom problems are very often cable problems. The device at the end is only where the symptom becomes audible.

That distinction matters because replacing equipment without understanding the cable path can waste time and money. The new handset may make the same noise as the old one if the signal cable is still running beside power, wrapped around the wrong cable, joined badly or sharing a route it should never have shared.

Voice signal is not the same as power

Intercom audio is sensitive.

It does not behave like a light circuit. It does not behave like a simple on/off trigger. It carries a low-voltage signal that can be affected by nearby electrical noise, poor separation, grounding issues, bad joins and cable choice.

One of the first questions DG Technologies asks when fault-finding noisy intercoms is simple:

Where does the cable run?

If the voice cable has been pulled in the same conduit as 220V power, or if it runs tightly alongside electrical cabling for long distances, the intercom may pick up noise. That noise can appear as a buzz, hum or unstable audio.

This is why low-voltage planning matters. Intercoms, data, CCTV, access control, audio, control wiring and mains power should not be treated as interchangeable cable routes. They each have different behaviour and different risks.

Twisted pairs matter

Many intercoms are wired using spare communication cabling such as Cat cable. That can work well, but only if the pairs are used sensibly.

A twisted pair is designed so the two conductors work together. If the installer randomly borrows individual wires from different pairs, the cable loses some of the benefit of the twist. On a short run, it may seem fine. On a longer run, or in a noisy electrical environment, it may create problems that are difficult to diagnose later.

This is the sort of detail that does not appear impressive on a quotation, but it matters on site.

A properly chosen pair, correctly terminated, routed away from power and documented, is part of the quality of the system.

Noise can come from the path, not the product

We have seen situations where the intercom still made noise even when the devices themselves appeared healthy. That is when the process becomes important.

A proper fault-finding sequence might include:

  • Testing the handset on a short temporary cable.
  • Checking whether the noise remains when the cable route is bypassed.
  • Confirming whether the intercom cable shares a conduit with mains power.
  • Looking for poor joins, damaged cable or water ingress.
  • Checking whether the device is using the correct pair arrangement.
  • Confirming power supply quality and grounding behaviour.
  • Separating signal and voltage where possible.

This avoids guessing.

If the unit is noisy on a two-metre test cable, the device or power supply may be suspect. If the unit is clean on a short cable but noisy through the installed route, the building wiring becomes the investigation.

Gate routes need special care

Gate and intercom wiring is often exposed to more abuse than internal house cabling.

It may run underground. It may pass through boundary walls, gate motor boxes, conduits with moisture, garden areas, paving, pool zones or electrical ducts. It may be near gate motor cabling, beams, strikes, maglocks, lights, cameras or electric fencing.

For a premium property, the gate is not just a convenience point. It is a security and communication point.

If that route is unreliable, the homeowner feels it immediately. Visitors cannot communicate properly. Remote opening becomes frustrating. Security staff may not hear clearly. The owner loses confidence in a system that should be simple.

That is why gate and intercom planning should sit beside access control, CCTV and network infrastructure, not as an afterthought.

Separation is cheaper than repair

The most frustrating low-voltage faults are often the ones that could have been avoided during first fix.

Before walls, ceilings and paving close, cable routing is relatively easy to correct. After finishes are complete, finding and replacing a noisy cable route can become disruptive.

Good planning asks:

  • Is the intercom route separate from mains power?
  • Is there a proper conduit path back to the head end or control point?
  • Are draw boxes accessible?
  • Is there a service route if the cable ever needs replacement?
  • Is the cable protected where it leaves the building?
  • Is the gate area planned with CCTV, access control and power together?

This is also why we keep pushing architects and builders to treat low-voltage planning as part of construction coordination. The cost of a proper conduit route is small compared with opening finishes later.

A premium intercom should be boring

The best intercom system is not the one with the most features.

It is the one the homeowner does not have to think about.

The call comes through clearly. The right person answers. The correct camera view is available. The gate opens when authorised. The audio is clean. The system remains serviceable years later.

To achieve that, the work behind the device has to be disciplined.

Cable separation, correct pairs, neat terminations, accessible draw points, sensible power supply decisions and documentation all matter.

When DG Technologies looks at an intercom problem, we do not only ask which handset is on the wall. We ask what is happening behind the wall, through the conduit, across the gate route and back at the head end.

That is usually where the truth sits.