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A dual SIM mobile phone is one which holds two SIM cards. Initially, dual-SIM adapters were made available to use in regular mobile phones to allow them to contain two SIMs, and to switch from one to the other as required. This combination is called a standby dual-SIM phone. More recently, some phones have been produced that can natively work with two SIMs, both of which may be active at the same time. These are active dual-SIM phones. There are also some Chinese triple-SIM phones[1].
Dual-SIM operation allows the use of two services without the need to carry two phones at the same time. For example, the same handset can be used for business and private use with separate numbers and bills; or for travel, with an additional SIM for the country visited.
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Standby dual-SIM phones
Several types of adapters are available. All of them allow only one SIM to be active, and to receive calls, at any given time; they provide various ways of switching from one SIM to the other. Earlier versions required the phone to be switched off and on again to change from one to another. Later models allow the user to switch SIM cards via a menu or by keying in a numeric code, without switching the phone off.
Some adapters require the two SIM cards to be cut to size, fitted onto a special holder and are inserted into the phone's SIM socket; this can be quite risky, since the user might end up damaging the SIM card in the process. Other adapters don't require cutting or modifying the SIM card. The adapter has two slots for the SIM cards, and a small ribbon cable, which is hooked to a PCB that mimics another SIM card. Because of the added circuitry, adapters for some phones, such as those used for older models, like the Nokia 3210 and Nokia 3310, often include thicker battery covers. Recent variations of this setup do away with the added bulk and has more miniaturized components, allowing owners of newer handsets to go to a dual SIM setup.
Active dual-SIM phones
Mobile phones with built-in simultaneous dual SIM capability have the advantage that there are no possible legal issues, breach of contract, or voiding of warranty. They allow both SIMs to be active simultaneously and allow calls to be received on either number at any given time.
Normal GSM phones contain a single transceiver; dual-SIM phones must have dual transceivers, and need to display signal strength for both networks. A phone with a single transceiver cannot be converted to simultaneous dual-SIM operation; at most it can be turned into a standby dual-SIM phone with the use of an adapter.
Although battery life (talk time and standby time) of active dual-SIM mobile phones is reduced — typically by about a third[citation needed] — when both SIMs are active, to compensate this they often came with better capacity batteries, or in the case of Chinese-made phones, bundle their units with two batteries, compared to single-SIM phones.
In November 2007, Verzio — a Singapore-based 3C (computing, communications, consumer electronics) brand launched the world's first 3G Dual-Triband dual-SIM model named Duplii. The same brand also launched the Twinn, 2.75G dual-SIM model. Powered by 2 processors, the Duplii and Twinn provide real dual-SIM real dual-connecting capability.
There are some little-known Chinese companies supplying inexpensive dual-SIM mobiles, mainly in Asian countries. The latest model includes an iPhone look alike which is the smallest dual-SIM phone ever built. However, these dual-SIM phones generally work on 1 processor only, thus operate with limited dual-SIM functions.
Philips has made models Xenium 9@9w and 699 with this capability belonging to the restart to change active-line generation. Samsung also released the D880 DuoS in November 2007, a slider which can hold two SIM cards with simultaneous standby and the D780 which came much later, and there is a Windows Mobile based dual-sim phone too, called E-TEN glofiish DX900 (released in November 2008, been renamed to Acer Tempo DX900 in January 2009, after Acer bought E-TEN).
See also
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