Cordless phone frequencies can determine clarity

With some variations, most phones operate on one of three frequencies: 2.4 GHz, 5.8 GHz or 1.9 GHz, the latter also known as Digital Enhanced Cordless Telecommunications (DECT). DECT is found on most new phones and almost completely eliminates interference.

Cordless phones on the 900 MHz frequency are becoming obsolete. With so many other electronics devices operating on the same frequency, 900 MHz cordless phones suffered from interference and static. The 900 MHz frequency is still sometimes used in combination with 5.8 GHz or 2.4 GHz phones that use digital spread spectrum (DSS) or "frequency hopping" technology.

The 2.4 GHz band is also crowded, because home Wi-Fi networks use this frequency. Some wireless stereo headphones and wireless game controllers also operate on the same frequencies, so 2.4 GHz phones can get interference from those devices as well. The 5.8 GHz band is less crowded, so you'll get less interference. For the least interference, choose one of the new DECT phones that operates on the 1.9 GHz band, which is reserved for cordless phones only. 

Digital phones are much more secure than analog phones because they scramble the signal from the phone to the receiver unit so calls can't be intercepted. DSS cordless phones digitize your voice, letting the signal carry over a slightly longer range, and offer added security by scrambling conversations across frequencies. In spread spectrum, the phone transmits and receives signals on several channels at once; if a signal is poor on one frequency, the clear signal on another frequency will compensate. Most 5.8 GHz cordless phones are DSS phones and so are a few 2.4 GHz models. DECT phones have their own system to prevent eavesdropping, using encryption and authentication from the handset to the receiver.

With analog cordless phones it's easy for anyone with a police scanner or similar monitor to intercept your calls. When people with baby monitors report that they can sometimes hear their neighbors' phone conversations, analog technology is the culprit. While analog phones used to be significantly cheaper than digital phones, that's no longer the case. Unless you live in a remote area and aren't at all concerned about someone accidentally or intentionally listening in, consider upgrading to a digital phone.

The following is what experts say about purchasing a cordless phone:

  • Today's cordless phones are smaller, making them easy to carry around, but more difficult to cradle on your shoulder. Remember that smaller phones also have smaller keypad buttons, which can make dialing difficult. Some cordless phones include a headset jack for hands-free use, but you'll most likely have to supply your own headset, which will cost you $10 to $30.
  • Look for a digital phone if you're concerned about security. Calls on analog phones can easily be intercepted by anyone with a scanner -- but most commonly, some parents report being able to hear their neighbors' conversations over their baby monitor. Also, phones with so-called digital base security aren't necessarily digital; all cordless phones have digital base security to keep other people from dialing through your phone line. Some manufacturers will advertise a phone as digital even if only its answering machine component is digital, so be careful and read the fine print. Digital phones include both DSS and DECT models.
  • Consider interference. You'll occasionally see 2.4 GHz and 5.8 GHz phones on store shelves, but phones that operate on the 1.9 GHz frequency are the least susceptible to interference, and they no longer cost much more than older-style phones. If you live in an apartment building or other populous area, keep in mind that you may get interference from wireless networks even if you don't have one yourself.
  • Almost all phones can be used with caller ID and as a speakerphone. Most new models are also expandable to include more handsets. Some have headphone jacks and belt clips for hands-free use.
  • Don't place the handset of a cordless phone back on its base after each call, experts say. Charging the battery too frequently will weaken its power and shorten its life. This may be less of a problem with nickel-metal hydride (NiMH) batteries than with nickel-cadmium (Ni-Cd) batteries. However, it is still a good practice to wait until the low-battery light indicates a recharge is needed. Also, using the phone in a high location within your home will usually increase reception. Positioning the base away from TVs, computers, microwave ovens or other cordless phones will help cut down on interference.
  • Batteries last from one to two years, depending on use. If your phone came with a Ni-Cd battery, you may want to consider replacing it with a more efficient (and slightly more expensive) NiMH battery. Some phones use proprietary battery packs and those can only accept direct replacements.

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