Overview
Why wired lines still matter
With wireless devices everywhere, checking cables can seem old-fashioned. Yet a cable is still an attractive route for eavesdropping: it supplies constant power, doesn’t transmit and so is invisible to RF, and lets someone listen from far away. A phone cable running from a boardroom to the distribution frame can carry audio out without anyone entering the room again. That is why line analysis complements RF and NLJD in a full office sweep.
What we check
- Landlines: taps and abnormal loads between the wall socket and the building’s demarcation point
- Desk phones and handsets: modifications that keep the microphone live with the handset down, and parts added inside
- Digital and IP desk phones: besides physical changes, settings such as forwarding or auto-answer that can be misused
- Intercoms and door phones: systems that can carry audio to another point in the building
- Spare conductors: idle pairs inside a cable and old lines described as “unused”
- Wall boxes, distribution frames and cable trays: the physical points where taps are most often made
Spare conductors deserve attention. A microphone wired to an idle pair can carry sound elsewhere in the building without transmitting anything or leaving an obvious device in the room.
How we measure
Line analysis combines electrical measurement with physical inspection. Measuring voltage, current and impedance shows points that deviate from normal; an unexpected load, leak or branch usually appears in the readings. Reflection measurement gives the approximate distance to a splice or branch, which we then check by hand. Desk phones and intercoms are opened, and NLJD and thermal imaging help reveal added circuitry or unexpected heat. At the frame, we document which line serves which room and trace every connection that doesn’t fit the map.
An honest limit
In-building line inspection cannot cover the carrier and network level. Once the line leaves the building, interception within the carrier’s infrastructure is invisible to any measurement we take inside. Mobile and internet calls are also outside this service; see our phone and network inspections. We say this up front because knowing what a line inspection can and cannot verify matters for your decisions.
Before the inspection
- Don’t discuss it over the suspected lines or on phones in the room.
- Contact us from another device.
- Have keys for frames and comms rooms, and any cabling plans, ready.
- If you’ve seen an unfamiliar connection in a frame or box, don’t touch or move it.
Report and recommendations
You receive the line map, measurements and findings in writing, along with recommendations such as decommissioning unused lines, restricting frame access and keeping a record of cabling changes. These also make any future inspection easier and more meaningful.
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Warning signs
- Unexplained crackling, clicks or volume changes during calls or with the handset down
- An extra connection in a distribution frame or wall box that nobody can account for
- A device attached to a cable said to be unused
- Signs that a desk phone or intercom has been opened
- Changes to building cabling that you didn't make
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Process
Mapping the infrastructure
With you and facilities, we map how phone, intercom, alarm and data lines run from each room to the distribution frame.
Electrical measurement
We measure voltage, current and impedance on the lines, looking for abnormal loads, taps or leakage.
Cable tracing
Splices, branches and taps are located by reflection measurement and checked physically.
Device and box inspection
Desk phones, handsets, intercom units, wall boxes and distribution frames are opened and inspected.
Report
You receive the line map, measurements, findings and recommendations on cabling practice in writing.
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What you receive
- Written report of the lines inspected, measurements and findings
- Location, photographs and connection details of any finding
- Recommendations on decommissioning unused lines and controlling frame access
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Limitations
- Interception at carrier or network level cannot be detected by in-building line measurement.
- Mobile calls and internet-based calls fall under device and network inspections, not this service.
- Sections outside the building or owned by the carrier can only be inspected up to the points we are allowed to access.
- The inspection shows the state of the lines at the time it was carried out.
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Questions
Can you tell from the line whether my phone is tapped?
We can find a tap on lines and equipment inside the building through measurement and physical inspection. No in-building measurement will reveal carrier-level interception, and it's important to be clear about that.
Do crackling and clicks mean I'm being listened to?
Usually not. Those sounds generally come from old cabling, loose connections or the network. Measuring to find the cause is still the right way to settle the question.
Is a line inspection enough on its own?
It is one part of an office sweep. Wireless transmitters or recorders in the room won't show up in line measurements, so it is usually planned together with an office sweep.