This guide explains the most common cell phone terms that you need to know when you are buying a cell phone on eBay. You should start by searching for a phone with the name of the wireless carrier (Cingular, Verizon, etc.) in the title. Once you have narrowed the search, the terms below will make sure the phone you select will work for you. If you find this guide helpful, please help others find it by clicking "Yes" below. Thanks for reading.
I will break the terms down as they relate to the wireless carriers.
Cingular Wireless & T Mobile -- The GSM Carriers
1. GSM: It stands for Global System for Mobile communications. It the system that Cingular Wireless and T Mobile uses in the United States and associated with cell phones that use sim cards (see definition of sim cards below). GSM is sometimes confused with GPS (see definition below under Verizon), however, they are very different. GSM relates to Cingular and T Mobile phones, GPS relates to CDMA phones that are used by Verizon and US Cellular.
2. Sim Card. A sim card is a little piece of plastic that has a memory chip on it. The chip contains information about your cell phone account as well as personal information like your phone book and other information. The benefit of a sim card is that they can be easily taken out of one phone and inserted into another GSM phone and the phone will be instantly active. Remember only GSM phones use Sim Cards and Cingular Wireless and T Mobile use exclusively GSM phones.
Sim Card Slot on the Cell Phone
Sim Card Inserted in Cell Phone
3. Locked or Unlocked. These terms are used to tell whether a cell phone will work with sim cards from different carriers. For example, if the GSM phone is unlocked it will work if you put an active T Mobile or Cingular sim card in it. If it is locked to Cingular you can only use a Cingular sim card, likewise, if it is locked to T Mobile you can only use it with T Mobile. Phones are generally locked, if you want an unlocked phone, look for one that specifically says it is unlocked.
4. World Phone. World Phone is a term that describes a GSM cell phone that works not only with the US wireless carriers like Cingular and T Mobile, but also works on GSM networks in other parts of the world. In the US, T Mobile uses exclusively the 1900 mghz band, Cingular uses both the 850 and 1900 mghz band. In Europe and Asia, they use the 900 and the 1800 mghz band. A World Phone will have at least one of the US bands and one of the other bands. Note: the phone has to be unlocked if you want to use it with a local wireless carrier while you are abroad.
5. Dual Band, Tri-Band, Quad Band. As it relates to GSM phones, a band is a GSM frequency that the phone works on. For instance a phone that works on the 850 and 1900 would be a Dual Band. If it works on all 4 GSM bands is is a Quad Band. World Phones are generally Tri-Bands or Quad Bands. The only issue here is that if you buy a Cingular Phone, you should get it with the 850 band as well as the 1900, they use both bands and you will get the best reception if your cell phone can receive both signals.
Verizon, Sprint, Alltel, US Cellular - - The CDMA Carriers
1. CDMA. It stands for Code-Division Multible Access and it is the technology that was developed by Qualcomm that is used by Verizon Wireless, Sprint, Alltel, US Cellular as well as MetroPCS, Qwest and a host of other carriers. Even thought it is spreading throughout the world it predominately in the United States, the rest of the world is predominately GSM.
2. GPS. As part of the Homeland Security Act of all things, all cell phones that are activated in the United States are supposed to have a GPS location device in them. Verizon was the first major carrier to enforce this provision and started requiring that all phones that they activate have this feature. It allows emergency personal locate you if you call in and that is the reason it is sometimes referred to as e911 compliant. If you are buying a phone for Verizon, Alltel, or US Cellular make sure the phone has this feature. Many of the older phones do not, so make sure it has it or they will not activate it. Sprint does not require it, however, they do have some of there own requirements (listed below).
3. Dual Mode, Tri-Mode. CDMA works on the 800 and 1900 mhtz bands and most all phones also work on an analog band as well. Thus, a CDMA phone that works on the analog, 800, and 1900 bands are called Tri-Mode. Unlike GSM phones when a CDMA phones works on more than one band it is referred to as a Mode not a Band. Verizon, Alltel and US Cellular require that all phones be Tri-Mode to be activated on their system. I am unaware of any GPS phone that is not Tri-Mode, however, a few Tri-Mode phones are not GPS. Many times the term GPS and Tri-Mode are used interchangeably and for the most part that is not a problem, however, Verizon, Alltel and US Cellular require both Tri-Mode and GPS. Sprint requires neither and works only off of the 1900 mhtz band, sometimes called the PCS band, hence Sprnt PCS.
4. E911. As stated above in the GPS definition, e911 means the phone has a GPS locator in the phone enabling emergency personal to locate your cell phone signal. US Cellular uses this term and requires that all phones be e911 compliant.
5. WLNP. Stands for Wireless Line Portability and is part of the law that requires cell phone carriers to allow their customers to keep their telephone number when they switch to another carrier. As it relates to purchasing a replacement cell phone, it is only relevant to Sprint. There is a peculiar aspect of Sprints programming that prevented some phones from being able to be reprogrammed. Some phones just can't be programmed to comply, some can be upgraded and some where manufactured with the ability. The only safe thing to do is to purchase a WLNP compliant phone for Sprint. Look for this designation when you buy a Sprint phone or call Sprint and ask if the model phone you are interested in is WLNP compliant.
6. ESN. Stands for Electronic Serial Number. It is the number that CDMA carriers use to keep up with your account including minutes used etc. GSM carriers use information contained on your sim card. If the phone is reported lost or stolen or the bill has not been paid by the prior owner, the carrier will block that esn and hence the phone from being used. Sprint is the most tenacious about this and look for a designation that the esn has been checked or ask for it and call on it yourself.
The ESN Number is Always Below the Battery
The ESN Number is on the Label
7. Roaming. Roaming means that your phone is unable to locate the wireless carrier provider (Verizon, US Cellular) and instead uses another network (US Cellular roams on Sprint when the phone can not find a US Cellular signal). When it is using another network the phone is deemed to be "Roaming". Some carriers charge you to Roam on other networks on some of the calling plans and not on other calling plans. Verizon's nationwide plan does not charge to roam. This is really not a phone purchasing issue, more of selecting a wireless calling plan issue.
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JustCellular on eBay.