Talk:Cordless telephone

some cordless phones have different GHz. Some have 2.4, 5.8, ect... which one is better and why?

2.4 GHz phones can suffer interference from microwave ovens and wireless computer networks. 5.8 GHz phones avoid this problem. LeoO3 00:21, 18 August 2005 (UTC)

Performance

I'm sure it's more complicated than "manufacturers say higher frequencies are better but they're not because anonymous editor says so".

• Yeah, phone bandwidth is very small, but you can use a wider-than-audio band FM, for instance, to get better range and less interference.
• What modulation schemes do these phones use? Digital? FM? frequency-hopping?
• Do they automatically switch frequencies within the band when they detect interference?
• How wide is each band?
• How much of the band can each phone take up, since they aren't likely to interfere at short range?
• How difficult is it to eavesdrop on each modulation scheme?
• etc. — Omegatron 20:58, 1 November 2005 (UTC)

Higher frequencies corresponds to shorter wavelengths, so deflection is less likely and the wave can be transmitted without great loss.

I am fairly certain that the above sentence relating to frequencies is opposite the truth. Higher frequencies thus shorter wavelenghts are more easily reflected and suffer many problems such as multi-path interference because of these reflections. That is why radar is high frequency, because it reflects off of just about any surface.

It is to most of our best interests to prevent our cordless phone conversation from traveling outside of our homes so this is not typically a concern.

Given equal transmission power levels a frequency of half can travel twice as far. A 900MHz phone should have almost 3 times the range if both phones transmitted with equal power.

Boilerbots 04:06, 28 February 2006 (UTC)

• Higher the frequency, the less crowded the airwaves, which is why 5.8GHz phones were invented. Less crowding at that spectrum, whereas 2.4GHz is shared by wifi, microwaves, etc; and 900MHz is shared by cellular phones. ~ crazytales56297 -talk- 18:37, 1 August 2006 (UTC)

Higher radio frequencies tend to suffer from shorter range. They are more prone to atmospheric attenuation, exhibit greater line of sight characteristics (attenuation from walls, vegetation) and are unable to benefit from surface wave diffraction (although nothing but the oldest cordless phones on the 27MHz band benefit from this). If all things were equal (Tx power, channel width and spacing, carrier modulation, background noise, antenna gain, spectrum spread), a 900 MHz system would still have greater range than a 2.4 or 5.8 GHz system. That being said, many newer handsets that do utilize 2.4 or 5.8 GHz bands tend to offer features (wideband channels, DSSS & OFDMA spread spectrum, etc...) that counterbalance the drawbacks of these bands. -- Dinjiin —Preceding unsigned comment added by 24.251.140.182 (talk) 06:31, 19 October 2007 (UTC)

Yeah. Lower frequencies are naturally better, but most radio transceivers don't live in a natural envivonment; they live in one polluted by other radios. Higher frequencies are often (not always) less polluted, and offer ways to cut through what pollution there is. Jim.henderson 20:23, 19 October 2007 (UTC)

Quality

"Most cordless telephones, though, no matter what frequency band or transmission method is used, will hardly ever exactly match the sound quality of a high-quality wired telephone attached to a good telephone line." It goes on to list some questionable concerns (things that applied to very old analog cordless phones, most likely). Aside from the quantization noise of a DA/AD trip, I think most of these issues have been addressed in the past decade. Can an engineer who's qualified address this? BillMcGonigle (talk) 00:10, 17 July 2009 (UTC)

Security

The security section of the article seems to focus on security during a call, however what of the situation where multiple users are in close proximity. How are digital cordless phones and base stations "locked" to make it impossible for a user to connect to their neighbours' base station? Or, for that matter, how are the phones "unlocked" so multiple cordless phones may communicate with a single base station (particularly useful in multiple storey houses, for example)? Maybe this could be addressed in the article. --ozzmosis 12:52, 4 June 2006 (UTC)

• I believe each phone has its own unique ‘transmission key’ - ie a message sent before the data packet. Also, different phones transmit on slightly different wavelengths - 5.800 vs 5.815GHz for example. ~ crazytales56297 -talk- 18:35, 1 August 2006 (UTC)

Higer frequencies better

This may or maynot be true, depending on the materials that may block the non LOS path to the base station the propagation effects vary. It is a known fact that we modulate and upconvert RF signals for what is known as ease of radiation. However, according to this PDF [1] and pages 14 and 15 of this PDF file [2] it appears that higher frequencies, paticularly the ones in debate actually have higher propagation losses through various common materials such as vegetation, walls, ect. As far as reflection goes, RF frequecy and light are on the EM Spectrum. As frequency increases there is a point in which radio signals behave like light. You can expect better propgation if you are using a parabolic reflector dishes like those found on SATCOM terminals; in this situation the higher the frequency, the better the gain. Also it may be noted that there is generally less spectrum congestion at 5.8 GHz, that might be caused by a WIFI device or microwave which operate at 2.4 GHz, for this frequency resulting in a lower noise floor allowing for a stronger power "peek".

( ( expand ) ) -- Still needed? Why?

It looks to me that the "((expand))") may no longer be necessary. The article, to me, appears fairly thorough. What are your opinions on it's removal? If you think removal is not appropriate, what do you think the article needs before removing this tag is appropriate? Dmcmorris 16:13, 11 October 2006 (UTC)

Picture

Is that main picture really appropriate?? I'm sure we can find something better. Any thoughts? Tingalex 22:24, 26 November 2006 (UTC)

The new one is much better quality and I assume to be appropriate. Darkshark0159 22:24, 12 June 2007 (UTC)

I think it's fine, but in the cell phone article it uses rather old phones as images. Maybe we could get a picture of more recent cell/mobile and cordless phone pictures. 68.51.41.46 (talk) 05:04, 14 February 2009 (UTC)

Battery

What kind of battery is used in cordless phones? Do they need to be recharged for 20 hours before they can be used? What happens if you try to recharge a cordless phone battery before its power is completely drained? Is that the memory effect where the battery will be broken for good and never be able to recharge completely anymore? How many years are the batteries good for? And do they pollute a lot when you throw them away to replace them? 206.47.141.21 18:54, 30 January 2007 (UTC)

Yes, ten years ago almost all were ni-cad which have the costs you list. Some other battery markets have shifted to li-ion which have different costs (like, sometimes they burst into flame) but I don't think cordless phones have shifted yet. I'm not sure enough to put it in the article. Jim.henderson 16:28, 3 February 2007 (UTC)

with a second (duo) cordless phone operating elsewhere in the house,away from the controlling set,does the power have to be plugged in ?...provided the 2nd phone is regularly exchanged with the original to keep battery life high ?Berniebg 07:19, 15 August 2007 (UTC)

Modern cordless use Ni-MH AAA 500-700mAH rechargeable batteries. But some manufacturers have made the mistake (or is it deliberate?) in designing the battery compartment too tightly around the positive end and only the supplied industrial type rechargeable will fit in it due to its slightly extended nipple. Others have a compartment with the usual spring and metal leaf and these will take the ordinary 700-1000mAH AAA rechargeables you can buy in any store. If you are swopping from a old 500mAH Ni-MH to a modern 1000mAH Ni-MH battery then these will take a few extra hours to charge. But otherwise they will work perfectly well and you'll get a longer talk time.

• Note: Don't swap a Ni-Cd type for a Ni-MH type. Their charging parameters are different and may damage the new Ni-MH type. Sadly Ni-Cd batteries are virtually obsolete these days so maybe time to get a new phone. --Quatermass (talk) 21:36, 26 September 2010 (UTC)

Health

I am interested in any possible health issues with cordless phones, especially compared to cell phones. Can anybody point to any studies that may have been done? Does anybody know the power output of a cordless phone compared to that of a cell phone?--SkiDragon 04:18, 20 July 2007 (UTC)

This could help and may be a seed for a new section in this article --Notopia (talk) 10:13, 11 August 2008 (UTC)

Incompatibile with wireless Internet ?

After enjoying the benefits of Cordless T. for nearly 15 years, we find it is appears incompatible with our new wireless modem ie it's impossible to hear anything useful, I presume b/c the T's radio signals conflict with those betweem modem and phone tower ! To have to regress to a cord phone seems like an unexpected & unpleasant option...any clues ? Feroshki (talk) 23:55, 9 December 2007 (UTC)

Feroshki (talk) 00:15, 14 December 2007 (UTC) to answer my own question, I see I should have read the very first entry [ untitled] in this Discussion article. Sorry ! BTW I see in the Phone store that new models make a point of listing themselves as "wifi friendly.."

"DECT 6.0" standard

Can someone please explain the "DECT 6.0" generation of phones? (Example: Uniden has one or more such models.)
What frequencie(s) does this type use?
I've been given the impression that they're not 5.8, but I just don't know.

Found this: Digital Enhanced Cordless Telecommunications#DECT_6.0

LP-mn (talk) 13:24, 16 June 2011 (UTC)
LP-mn (talk) 15:11, 16 June 2011 (UTC)

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