Cordless phone and cellular phone can work closely?

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maolh

Joined: 16 Jun 2003
Posts: 39

04 Nov 2003 18:00 Cordless phone and cellular phone can work closely?

There is a stupid question bothering me. Say, there is cordless phone marked with 900MHz, also a GSM900 cell phone. Both of them use the same RF band which is centered at about 900MHz. If they are used in the same room, i.e. using the cordless phone call the cell phone, do you think there is no problem for this phone call? And why?

Thanks.

flatulent

Joined: 19 Jul 2002
Posts: 4875
Helped: 324
Location: Middle Earth

04 Nov 2003 18:03 different frequencies

They are on different frequencies. That is assuming that you bought both items in the same country.

What you may find is that the cordless phone is probably lower quality and may have blocking problems from a strong out of band signal from your GSM device.

pool_77

Joined: 08 Aug 2001
Posts: 220

04 Nov 2003 18:59 Re: Cordless phone and cellular phone can work closely?

cordless phones on 900MHz use narrow FM. It is CT-1 or CT-1+ standard
pool_77

mr_ghz

Joined: 01 Apr 2002
Posts: 294
Helped: 2

04 Nov 2003 20:24 Re: Cordless phone and cellular phone can work closely?

Hi maolh

As written above the phones use different frequency bands so they should not interfere each other. It's possible that the cordless phone is more sensitive to a large out of band signal received from a near GSM phone. So theoretically you can hear some noise in your cordless phone coming from the GSM even when they use different frequencies. When the distance of both phones is more than some meters you should hear no interference (if the quality of your phones is not too bad...)

Bye

maolh

Joined: 16 Jun 2003
Posts: 39

04 Nov 2003 20:51 Re: Cordless phone and cellular phone can work closely?

I appreciate all you guys for your helpful replies. I got your point: they work at different frequency band. As I know, GSM900 is between 935 to 960MHz, how about the cordless standard?

The following is excerpted from Panasonic website(http://www.panasonic.com/consumer_electronics/telephones/900mhz_phones.asp) :

Digital Spread Spectrum Technology (SST)
Our 900 MHz phones utilize Digital Spread Spectrum technology to provide two important benefits for your home or home office: enhanced range and security. These phones transmit over the entire 900 MHz bandwidth, constantly changing frequencies to boost calling range, keep your conversations clear and make them very difficult for outside parties to monitor.

It mentioned that "These phones transmit over the entire 900 MHz bandwidth", what does this mean? Is the whole band 900MHz wide? or the center frequence of the carrier is 900MHz? how can the phone use "the entire 900 MHz bandwidth"?

flatulent

Joined: 19 Jul 2002
Posts: 4875
Helped: 324
Location: Middle Earth

04 Nov 2003 21:12 ISM band

Cordless phones work in the ISM band which is around 902-928 or so.

hugo_nz

Joined: 20 Jul 2003
Posts: 52

05 Nov 2003 4:20 Re: Cordless phone and cellular phone can work closely?

what about DECt what band does that work on. is it spread spectrum? where can i find more info on it.

riz_aj

Joined: 05 Feb 2002
Posts: 108
Helped: 1

05 Nov 2003 6:23 Re: Cordless phone and cellular phone can work closely?

Here are some links. Don't think that it is spread spectrum.

www.dectweb.com/

DECT Forum
www.dect.org/

www.etsi.org/technicalactiv/DECT/dect.htm

artem

Joined: 22 May 2003
Posts: 1652
Helped: 91
Location: Turan

05 Nov 2003 14:04

The frequenies for GSM (including extended and additional GSM ) :
uplink 876-915
downlink 921-960

Primary GSM band uses :
uplink 890 -915
downlink 935-960

Also there is also frequency hopping feature with predefined pseudorandom sequences numbered from 0 to 63 .

superman

Joined: 18 Feb 2003
Posts: 4

02 Dec 2003 13:36 Re: Cordless phone and cellular phone can work closely?

DECT is not DSSS instead the modulation scheme is MC-TDMA-FD
stands for multi carrier time devision multiple access full duplex
frequence band is 1.88 Ghz
10 carriers / 12 time channel per one carrier

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02 Dec 2003 13:36 Ads

northguy

Joined: 14 Nov 2003
Posts: 22

03 Dec 2003 6:46 Re: Cordless phone and cellular phone can work closely?

I try it before,there was a little bit noise from cordless phone.

superluminal

Joined: 31 Jan 2002
Posts: 95
Helped: 1
Location: Inside a quantum well

03 Dec 2003 12:56 Re: Cordless phone and cellular phone can work closely?

Cordless phones use the entire band by just changing there assigned channel from the "base" set to your handset. In these phones there is a small button that will momentarly change the channel when you push it , even when you are talking. It uses FM in most cases.

I don't know really if they will be affected by GSM phones ! I have one cordless phone working at 2.4 GHz , the ISM band. The microwave oven should emit some energy in this band ! But it is hard to test in home.