There are different systems that cordless phones use for the wireless communication between handset and base. Probably the most common is DECT and its derivatives.

The DECT system was designed in Europe and is used by several manufacturers. The phones operate in a reserved 1.8GHz frequency band, so they don't suffer from interference from other wireless devices like WiFi networks. They are designed to have a range of around 50 metres.

We think the best system is DECT-GAP. This stands for – take a deep breath – Digital Enhanced Cordless Telecommunications, Generic Access Profile-compliant. The beauty of these phones is you can mix and match handsets and base stations of different makes and models, You can also transfer calls between handsets, and handsets can be registered to more than one base station. Not all DECT phones are GAP-compliant, however.

DECT 6.0 is a US version of DECT that operates in a slightly different (but still reserved) 1.9GHz frequency band. It's otherwise similar to DECT, but that frequency difference means the two systems are not compatible..

XDECT is a proprietary (Uniden) version of DECT that claims greater range.

5.8GHz phones use proprietary frequency-hopping technology. These phones are not related to DECT and often have a shorter range – especially through building obstacles.

Other factors

Recharging
Phones use Nicad or nickel metal hydride (NiMH) batteries. Nicads are said to suffer from a "memory" effect – if you recharge them before they are fully run down, they may only use the new store of energy before needing to be recharged again.

NiMH batteries don't have this problem. They also contain less heavy metals and are a lower environmental risk when disposed of in landfills.

Type of batteries
We like standard-sized "AAA" (NiMH) rechargeable batteries. When the batteries finally fail, replacements are available in most supermarkets and other outlets. With a custom battery-pack, a replacement can be difficult to find – and possibly more expensive.

Range
If you have a big garden or a sprawling house, choose a phone with a good range score. Remember that trees, wire fences and solid walls all reduce range. (See Extra long range for more information.)

Talk time
Most handsets give between 10 and 20 hours of talk time. That's plenty, but make sure you replace the phone in the base station after a long chat. Standby time can be up to a fortnight or so.

Security
Digital phone conversations are encrypted and very secure. If you use telephone banking, make sure you delete the call memory after each banking session, so you do not leave behind sensitive numbers like your PIN.

Phone size
Small phones are easy to carry around, but larger models are more comfortable to use, especially for longer conversations.

Ease of use
Look for good-sized buttons, preferably backlit, with clear labels. Watch out for numbers made hard to read by a lack of contrast (for example, grey numbers on a grey background).

Try the handset to ensure it's not too heavy, is comfortable to hold, and fits well against your ear. Physical design is especially important for elderly or disabled users.

Telepermit
Look for a Telepermit sticker, which certifies compliance with local network connection requirements.

Electromagnetic radiation
Is radiation an issue for cordless phones? To date no clear evidence of a problem for mobiles or cordless phones has emerged. If you still want to limit your risk, use a wired phone for long conversations.

Interference
To avoid interference we recommend DECT 1.8GHz phones. This frequency isn’t used by other products and so it avoids interference from wireless networks, computers, home security systems and domestic appliances.

Analogue phones

Analogue models have been superseded by digital. They have fewer features than digital models, you won't get advanced options like multiple handsets, and privacy isn't guaranteed.

Features

Standard features

Many models on the market have a handset ringer with a redial key (and redial options), an alpha-numeric keypad, paging from base to handset, intercom, and favourite number storage.

Assistance for vision or hearing impairment

Features such as large buttons and display screens, extra-loud audio, hearing-aid compatibility, and slow replay of recorded messages are available.

Other features

Answering machine
The extra cost of a model with built-in answering machine can be recouped within a year compared with the cost of paying a phone company for voicemail.

Message indicator light
If you use your phone company's message service, a message light is useful.

Bluetooth connectivity
Lets you connect up to two bluetooth-equipped mobiles to your cordless system – so you can use your mobile to make and take landline calls as long as it’s within bluetooth range of the base-station.

Speaker phone
This lets you use the phone hands-free - a good feature when you're hands-on in the kitchen. It's also handy if you've got a crowd who want to listen.

Multiple handset option
Lets you register other handsets to the base station, though only one outside call can be made at a time. Multiple handsets can also be used as intercoms. With GAP-compliant DECT phones the handsets can be of different makes (see the Checklist for more about DECT-GAP).

Sometimes you can get a "pack" with at least one extra handset for not much more than you'll pay for a single phone. If you have a two-storey house – or a home office or work area – having more than one phone can be handy.

Corded phones
A corded phone in the base station lets you make calls during a power cut – useful if you don’t already have another corded phone or a mobile.

Caller ID
Lets you see the phone number of the caller, before you answer. The caller's name can also be displayed, if their details are in the phone's directory.

Headset port
Allows wearing a headset as another form of hands-free phoning.

No external antenna
A phone without an antenna will fit in your pocket without snagging, and is less susceptible to damage.

Belt clips
Attaches to the back of your phone. Useful if you are on the move around the house.

Baby monitor
Allows monitoring of sounds in another room, such as a baby crying.

Adaptors
Most models come with a low-voltage, plug-in power adaptor. A safety approval number on the adaptor shows compliance with electrical safety requirements.

Conversation recording
Digitally records conversation – especially useful for taking notes during phone meetings.