Phones with single mode:
will work only with one particular digital signal format and frequency.
For example, a phone that works only on an 800 MHz frequency TDMA network.
Such a phone might be suitable for people who do not call outside of their home calling area.
However, the phone will also work in a different area that has a network with the same digital signal format and frequency.
Phones with dual mode:
is single mode, plus will also work with an analog signal system.
A dual-mode phone has the capability to be used just about anywhere.
Whenever the digital network is not available, the phone can switch over to an analog network.
Dual-mode or tri-mode(see next) phones might be suitable if you will be traveling or spending a lot of time in areas where digital service in not available.
Phones with tri mode:
is dual mode that works on two frequencies (e.g. 800 and 1900 MHz) with one digital format (e.g. TDMA).
Working on 2 frequencies with one signal format is called dual-band.
So a tri-mode phone works on three frequencies: 2 digital and 1 analog.
EXPLAINATIONS:
Signal format and frequency.
A digital network uses one of three formats:
- code division multiple access (CDMA)
- time division multiple access (TDMA) or
- global system for mobile communications (GSM)
- integrated digital enhanced network (iDEN).
TDMA
A communications technique that uses a common channel (multipoint or broadcast) for communications among multiple users by allocating unique time slots to different users.
CDMA
A coding scheme, used as a modulation technique, in which multiple channels are independently coded for transmission over a single wideband channel.
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GSM
A public all-digital cellular network using TDMA techniques for multiplexing and using a transmission band around 900 MHz. GSM formerly identified the Groupe Speciale Mobile of the European Telecommunication Standards Institute (ETSI); today it is a worldwide standard. A GSM network can provide, besides telephony services, short messaging services (SMS) and data communication, in circuit- and/or packet mode. GSM signaling uses specific channels and protocols; voice is compressed at about 13 kb/s and error correcting algorithms (FEC) are used. The core network is based on a 64 kb/s circuit-switching technology. A more recent version uses an 1800 MHz band; modern terminals currently used in Europe can access both networks depending on traffic conditions and other parameters. A GSM version using a 1900 MHz access network is available in the United States.
iDEN
A specialized system that combines a TDMA phone with a two-way radio feature.
ANALOG SIGNAL
It's the traditional method of modulating radio signals.
A signal that has a continuous nature rather than a pulsed or discrete nature. (electrical or physical analogies, such as continuously varying voltages, frequencies, or phases, may be used as analog signals).
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