It’s bad enough that buying a cellular phone and wireless network->4 ing equipment is so complicated. Now, with new options for cordless phones, even that once straightforward purchase is forcing you to reach for the aspirin. Consider me the aspirin — and you don’t even have to call me in the morning. In this topic I discuss the different kinds of cordless phones, the advantages of one over the other, and a technology term or two.
You have choices when it comes to buying a cell phone and choices when installing wireless networking. Now, consider your standard telephone: when you decide to cut its cord and go wireless, you also have choices. Thankfully, cordless phones aren’t nearly as complex as smartphones or Wi-Fi networks, but there are different types of cordless phones that use various technologies.
Cutting the Cords
If you’re over 35, you probably remember the days when one of the only telephones in the house was a corded model mounted on the wall, possibly with a rotary dial. The only way to increase your distance from the phone was to purchase a longer cord. Although it might be possible, wrestling with a 300-foot cord so you can chat as you move from the kitchen to the garden to the garage is a bit impractical.
Around 1990, when the FCC assigned bandwidth in the 900 MHz frequency range, cordless phones first became a real alternative to corded telephones. While there were cordless phones before that (usually with big, metal, telescoping antennae), the newer frequencies were a big jump in clarity and range from the old 43-49 MHz band.
As manufacturers began making digital models, cordless phones grew even more practical; they were more secure (allowing for less eavesdropping) than analog versions. Also, more channels are available for use by the cordless phone to communicate between the base station and handset. A wider range of channels means interference is more easily thwarted. The breakdown is as follows:
♦ 10 to 25 channels for inexpensive 900 MHz phones.
♦ 20 to 60 channels for most 900 MHz phones.
♦ 50 to 100 channels for high-end 900 MHz phones and for 2.4 and 5.8 GHz phones.
Table 1-1 breaks down the megahertz and gigahertz by range.
Table 1-1: Cordless Phone Ranges
|
Frequency Band |
Range |
|
900 MHz |
75 to 400 feet |
|
900 MHz with DSS |
200 to 1,500 feet |
|
2.4 GHz with DSS |
300 to 2,000 feet |
|
5.8 GHz with DSS |
300 to 2,000 feet |
Analog phones
Analog cordless phones act like a plain, old AM/FM radio. They convert sounds waves into radio waves, transmitting them between the cordless phone and its base station. Anyone with a converter and a radio scanner can eavesdrop. (Selling police and fire radio scanners that pick up 900 MHz transmissions is illegal; 2.4 GHz and 5.8 GHz phones are out of range of most radio scanners.)
When you and an analog handset get too far from the base station, you hear static over the conversation until you can no longer communicate with the base station. These phones also are prone to static from interference. Figure 1-1 shows analog versus digital communications methods.
What is this DSS?
Many new cordless phones — and I recommend making sure this is true of the one you purchase next — use a technology called DSS, or digital spread spectrum. The digital part of DSS means your conversation is converted from analog sound waves to digital 1s and 0s. (You can buy a digital phone that does not use DSS, however.) The spread spectrum part is less clear, though it has something to do with the radio spectrum. This technical term is vague until you discover what it is, how it works, and why you want it.
First, why you want it: DSS-equipped phones are much more secure than analog and plain digital phones. In fact, it’s nearly impossible to listen to a conversation taking place on a DSS phone because the listener only hears quick bursts of data that transmit very quickly across multiple frequencies. In other words, one data burst will be at frequency A, then next at B, and so on — and only the phone knows what frequency the next data burst will occur on. Everything happens so fast that it’s impossible to follow conversations sent with DSS unless the eavesdropper has very expensive and sophisticated snooping equipment. You can feel pretty confident that the personal information you reveal during a telephone call (credit card numbers, social security numbers, and so on) on this phone is safe.
Second, phones using DSS suffer from less interference. Depending on different factors, they may also have a greater range than similar phones that don’t use DSS technology. In addition to being more secure, DSS is a more efficient use of the radio spectrum.
A DSS phone may also be referred to by frequency hopping spread spectrum or FHSS.
Figure 1-1:
Analog and digital phones work differently.
Digital phones
Digital phones convert sound waves into digital signals, which consist of a lot of 1s and 0s. If you tune into a conversation transmitted digitally, you can’t hear it without using equipment that converts the output into something humans can understand. When you go out of range with a digital phone, the conversation terminates suddenly with dead air. Digital phones offer no gray area between a good signal and a lousy signal. Their existence shows up on the time lines in Figure 1-2.
Figure 1-2:
A time line of cordless phone frequency band use.
Some digital phones use something called digital spread spectrum (DSS). See the "What is this DSS?" sidebar in this topic for further information. Not all digital phones have DSS, but all DSS phones are digital.
Choosing Your Frequency
Can you imagine if when purchasing a cell phone and a calling plan, you had to tell the company what technology you want to use? Of course, you have some choices when it comes to handsets and choosing a particular carrier for its network. You don’t have to tell the cell phone provider at what frequency you want the phone to operate.
When you purchase a cell phone and calling plan, you make some technical decisions. These mainly concern the handset and its features, plus a carrier for the network. Cordless phone shoppers have their own set of technological decisions to make, above and beyond the features offered by the model.
When shopping for cordless phones, you choose the frequency and sometimes whether the radio signals are analog or digital. Shopping for the phones in a store does little to narrow your decision making, other than deciding on the look and feel of the phone. Table 1-2 can help you start your comparison shopping before you set foot in a store.
Table 1-2: Pros and Cons of Cordless Frequency Bands
|
Band |
Pros |
Cons |
|
900 MHz |
Cheap, won’t interfere with Wi-Fi |
Usually little or no security, limited range |
|
2.4 GHz |
Price is right, more secure |
Possible conflicts with |
|
than 900 MHz secure |
Wi-Fi |
|
|
5.8 GHz |
Clear, likely more secure |
More expensive |
You have an array of choices when purchasing a cordless phone. The important option is the frequency band on which the phones operates. Cordless phones are available in 900 MHz, 2.4 GHz, and 5.8 GHz models. Generally, as the frequency goes higher, so does the maximum distance you can take the handset from the base station, and the clarity gets better. Watch out, however, for interference from other sources of radio waves, physical structures like walls, and the weather.
Here are what the three frequency bands offer.
900 MHz
You can buy one of these phones pretty cheaply, but many manufacturers are phasing them out, favoring instead the 2.4 GHz and 5.8 GHz models. If you’re on a budget, you can buy one of these analog models for less than you paid for this topic — but I wouldn’t recommend it.
Why? The prices of 2.4 GHz phones are very reasonable and cover a larger area with less likelihood of interference. Also, higher frequency phones offer more conversation security: It’s fairly simple to listen in to a 900 MHz analog signal with the right equipment.
2.4 GHz
Quality and price meet here. This is the sweet spot for cordless phones; most of them made today operate in this frequency range. They offer more clarity and range than you get with a 900 MHz phone.
Given the number of 2.4 GHz models, you can find them in a wide variety of configurations, choosing the features you want and not paying for ones you don’t need. You can buy 2.4 GHz phones in analog and digital models. These phones are also available in multiple-handset models, which let you add more handsets as you need them. Some models let you have as many as eight — seemingly enough for every room of your house. While the additional phones need a nearby AC outlet, they don’t each need a phone jack.
You can find 2.4GHz phones in a huge variety of configurations with any number of features. Some contain digital answering machines. Some allow you to add up to eight handsets to the same base. Extra handsets usually come with a charging dock for which you need an AC connection, but you only need a phone jack for the base station itself.
Unfortunately, phones that operate in the 2.4 GHz range can interfere with some Wi-Fi wireless networks (802.11b and 802.11g, but not 802.11a or 802.11n).
5.8 GHz
These phones have an exceptionally notable advantage over the other two kinds of phones: The 5.8 GHz band is less populated, but that’s changing quickly. Along with an increase in clarity and distance, cordless phones using this frequency are the perfect fit for a home that has a Wi-Fi network and other interference on the 2.4 GHz band.
The 5.8 GHz phones tend to be feature-packed affairs that get expensive quickly, although with the frequency growing in popularity it’s only a matter of time before cheaper 5.8 GHz phones emerge.
Featuring Cordless Phones
If the confusion over frequencies isn’t bad enough, you have to decide between a myriad of features when shopping for a cordless phone. From caller ID displays to multiple-handset models, you have much to discover before plopping down your greenbacks.
You find some of the features on cordless phones:
♦ Caller ID. If you subscribe to caller ID service through your local phone company, this feature is a must. If the phone’s not enabled for caller ID, subscribing doesn’t make any difference. When you get an incoming call, the caller’s phone number and possibly the name (if you pay for this service) appears on the handset’s display.
♦ Call waiting ID. Call waiting ID is a cool feature. While you’re on the phone with someone else, you can see who is trying to reach you by glancing at the display on your phone. If you want to take the new call, you flash over to the other line. When you’re done, if the first caller is still waiting, you can flash back to him or her.
♦ Digital answering machine. I thought everyone who needs to record calls signed up for voicemail through their phone company. I guess not. Long gone are the days of cassette tapes; the answering machines built into these phones are digital, which have far less recording capacity. One benefit is that long-winded callers have fewer seconds to leave their messages, sparing you some rambling. Sometimes you can even set the length of messages your answering machine will take before cutting off the caller.
♦ Multiple handsets. You can do several things with these phones:
• Add up to eight handsets (depending on the model) for use throughout your home.
• Answer a call using any one of the phones.
• Transfer a call to and from a handset.
• Page a handset, making the setup similar to an intercom system.
• Plug each handset’s cradle into a power outlet; they don’t require separate phone jacks.
♦ Two-line phones. These models can handle multiple phone lines. If you have a second line in your home, consider this feature. My household uses a two-line phone — one for business and faxing and the other for personal calls.
♦ Speakerphone. This feature is always handy, especially when stuck on hold with a credit card company or other sadistic entity. You can push the appropriate button and leave the handset in its cradle, using the speakerphone located in the base station. Better still are handsets with speakerphone built-in; you can carry them around and have speaker-phone conversations while you do other stuff.
Avoiding Interference
As I mentioned earlier, if you have a Wi-Fi network in your house, I don’t recommend the purchase of a 2.4 GHz cordless phone. If your household is constantly using a baby monitor, that could be a problem, too. Even microwave ovens, which operate on the same frequency, can create problems. Never situate the base of your phone near a microwave, because if somebody decides to heat up last night’s dinner while you’re on the phone, you’ll experience loud and annoying interference.
If your analog phone has interference, you hear it as static and hisses. A digital phone will probably fade in and out or have a shorter range, or even cough up sounds like buzzing or beeping (but not technically static).
The best way to eliminate or reduce these kinds of interference problems is to move the phone’s base station around the house, seeing if a different location makes any difference. If you already have a Wi-Fi network and purchased a 2.4 GHz phone without reading my wise admonitions beforehand, you still have hope. Just turn off the network when you’re using the phone and vice versa (as annoying as that can be). However, you may find the two coexist peacefully.
