How to find devices on your phone line
Why this matters
Many households and small businesses have devices connected to the phone line that they do not think about day to day. When the phone service moves to digital voice, anything that uses the old analogue line could stop working, sometimes silently, with no warning.
The first step is to find out what you actually have. This guide walks you through how to check.
Room-by-room walkthrough
The easiest way to find everything is to check each room in order. Start at the front door and work your way through the house.
Hallway and entrance
This is where the main phone socket usually is: a white box on the wall, often near the front door. Look at what is plugged into it:
- A phone cable going to the broadband router: normal for most broadband setups
- A phone cable going to a phone: a landline phone connected directly to the wall socket
- A splitter or filter with multiple cables: this may be connecting several devices to the phone line
- Nothing: you may not use the phone line at all, or the connection may be in another room
Also check for a telecare base unit (small white or grey box, often with a red button on top) and any door entry intercom panel.
Living room
Look for a cordless phone base station (usually on a side table or shelf, with a charging cradle), and any secondary phone sockets on the wall with devices plugged in.
Bedroom
Check for a telecare base unit or pull cord. These are common in bedrooms, particularly for people who have had falls. A pendant alarm talks wirelessly to the base unit, which then uses the phone line to call the monitoring centre.
Kitchen or utility room
The broadband router is often here. Check the back of the router for ports labelled "Phone" or "Tel". Anything plugged into these ports is already using digital voice.
Home office or study
Look for fax machines, separate phone lines for business use, and any payment terminals (card machines). Some home workers have a second phone line that may also be affected.
Cupboard or garage
The burglar alarm panel is often in an under-stairs cupboard or utility area. Follow the cables from it. If one leads to the phone socket, the alarm uses the phone line to communicate with the monitoring centre. There may also be a separate box labelled "communicator" or "dialler".
If you have a full-fibre (FTTP) connection, there may be no phone socket in use. Instead, look at the fibre box (ONT) and router for phone ports.
Common devices to look for
Here is a full list of things that commonly connect to the phone line. If you find any of these, add them to your list:
- Phones: corded or cordless base stations
- A telecare unit or personal alarm: usually a small box with a red button, sometimes near the front door or in the bedroom. The pendant or wristband talks to this box wirelessly.
- A burglar alarm communicator: a cable running from the alarm panel to the phone socket. Often a separate box from the main alarm panel.
- A fire alarm communicator: similar to above, often in commercial premises or blocks of flats
- A fax machine: still used in some offices and medical practices
- A payment terminal: card machines in shops that dial out over the phone line. Most modern ones use mobile or broadband, but older ones use PSTN.
- A door entry system or intercom: some connect to the phone line so you can buzz visitors in remotely
- A monitored CCTV system: some older systems send alerts via the phone line
- A lift emergency phone: in blocks of flats, the lift phone may use the building's phone line
Check the alarm panel
If you have a burglar alarm or fire alarm, look at the control panel (usually a metal box in a cupboard or utility room). Follow the cables coming out of it. If one goes to a phone socket or phone line junction, the alarm uses the phone line to communicate.
There may also be a separate small box labelled "communicator", "dialler", or "signalling device". This is the part that talks to the monitoring centre.
Check for telecare
A telecare unit is often a small white or grey box connected to both the phone line and mains power. It may have a red button on top. A pendant alarm or wrist button communicates with this box wirelessly, and the box then uses the phone line to call the monitoring centre.
If you or someone you care for wears a pendant alarm, follow the cable from the base unit to see if it connects to the phone socket or the router.
Look at the router
Modern routers often have one or two phone ports on the back (usually labelled "Phone 1" or "Tel"). If a phone or other device is plugged into these ports, it is using digital voice. It goes through the broadband connection, not the old analogue line.
Devices plugged into the router's phone ports may still be affected by power cuts (because they depend on the router having power), but they are already using the digital path.
Make a list
Write down everything you find that connects to the phone line or the router's phone ports. For each item, note:
- What it is (phone, alarm, telecare unit, etc.)
- Where it connects (wall phone socket, router phone port, or both)
- Whether it has its own mains power supply
- The make and model (usually on a label on the bottom or back)
- The name of the company that installed or monitors it (if applicable)
This list is what you need when you contact your phone provider or alarm company to ask about compatibility.
If you are checking for someone else
If you are helping a relative, neighbour, or tenant:
- Ask them before moving or unplugging anything
- Take photos of the connections before and after, so you can put things back
- If they have telecare, contact the telecare provider before making any changes to the phone line
- Write the list down on paper as well as digitally. The person may need it if you are not there
Next step
Once you have your list, use the device risk checker to find out which devices are affected and what to do about each one.