Mobile phone shop provides what they have at least some cell phone users eagerly desired for years, namely to operate two SIM cards simultaneously in one phone. In the 90s, a dual-SIM phone would have been interesting especially if you often resided in areas with changing radio coverage. The GSM networks at the time were not yet developed so well that she almost any place would have been available. Especially in rural areas is often came through regions where there were maybe only one or two networks available.
The interest on the parallel use of two SIM cards for years and carries the industry's needs. First there were mobile phone batteries, who received a second SIM. In the first devices had to be still off and go again to switch the phone between the two cards. Later, this battery possessed of little switches. Finally, it was also higher electronic systems; the SIM Application Tool kit menu generated by the user could switch between the two cards.
The mobile phone (dual SIM) uses two transmitting and receiving devices in a device to be available simultaneously on two lines (SIM cards). This is technically a trivial task, but many manufacturers produce mobile phones with a SIM card only, because the demand is so great. For sales representatives and sales abroad are often employed, the variant cell phone with two SIM cards is optimal. These can also use a foreign SIM card in the phone without the phone or the SIM card change.